Optical layer, method for producing optical layer, optical layer-provided solar cell module, outer wall material for building, and building

ABSTRACT

To provide a colored optical layer capable of forming a solar cell module excellent in the design, and the power generation efficiency and the weather resistance, a method for producing an optical layer, an optical layer-provided solar cell module, an outer wall material for building, and a building. 
     An optical layer having a functional layer containing an inorganic pigment and a matrix in which the inorganic pigment is dispersed, to be disposed on the side of plane of incidence of sunlight from solar cells, 
     wherein at least a part of the inorganic pigment is an inorganic pigment having a maximum near infrared reflectance in a near infrared region at a wavelength of from 780 to 1,500 nm of at least 50%, an average particle size of from 5.0 to 280.0 nm and a specific surface area of from 5.0 to 1,000 m 2 /g.

TECHNICAL FIELD

The present invention relates to an optical layer, a method forproducing an optical layer, an optical layer-provided solar cell module,an outer wall material for building, and a building.

BACKGROUND ART

In view of cost reduction and effective use of energy in power supply,installation of a solar cell module has been studied. In general, asolar cell module secures a power generation efficiency by using amember having a high sunlight transmittance. However, in such a case,solar cells are visually observed and can hardly harmonize withsurroundings in the aspect of outer appearance in many cases.

In order to solve such a problem, attempts are being made to partiallycolor members of a solar cell module thereby to improve the design.Patent Document 1 discloses an invention relating to a weather resistantcolor-toned film having a weather resistant transparent resin layer anda colored ethylene/vinyl acetate resin layer laminated and integrated,in order to impart the design to a solar cell module and to maintain thedesign over a long period of time.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP-A-2001-047568

DISCLOSURE OF INVENTION Technical Problem

However, the present inventors have found that if the design is impartedby coloring members of a solar cell module with e.g. a coloring agent,the sunlight transmittance may decrease in some cases depending upon thecoloring agent used. Specifically, in the above case, the powergeneration efficiency of the solar cell module is inferior to a casewhere the members are not colored. Further, the coloring agent itselfmay be deteriorated by sunlight, thus lowering the weather resistance ofthe solar cell module. Accordingly, it has been difficult to realize asolar cell module excellent in both the design, and the power generationefficiency and the weather resistance.

Under these circumstances, it is an object of the present invention toprovide an optical layer capable of forming a solar cell moduleexcellent in the design, and the power generation efficiency and theweather resistance, a method for producing an optical layer, an opticallayer-provided solar cell module, an outer wall material for building,and a building.

Solution to Problem

The present inventors have conducted extensive studies to achieve theabove objects and as a result, found that desired effects can beobtained by disposing an optical layer comprising a functional layercontaining an inorganic pigment having predetermined physical propertiesand a matrix in which the inorganic pigment is dispersed, on the side ofplane of incidence of sunlight of solar cells, and accomplished thepresent invention.

That is, the present inventors have found that the above objects can beachieved by the following constitutions.

[1] An optical layer comprising a functional layer containing aninorganic pigment and a matrix in which the inorganic pigment isdispersed, to be disposed on the side of plane of incidence of sunlightof solar cells,

wherein at least a part of the inorganic pigment is an inorganic pigmenthaving a maximum near infrared reflectance in a near infrared region ata wavelength of from 780 to 1,500 nm of at least 50%, an averageparticle size of from 5.0 to 280.0 nm and a specific surface area offrom 5.0 to 1,000 m²/g.

[2] The optical layer according to [1], wherein the optical layer is acolored optical layer, and the above specific inorganic pigment is acolored inorganic pigment.[3] The optical layer according to [2], wherein the colored inorganicpigment is an inorganic pigment having in the L*a*b* color space an L*value of from 5 to 100, an a* value of from −60 to 60, and a b* value offrom −60 to 60.[4] The optical layer according to [2] or [3], which further contains alight scattering inorganic pigment (excluding the colored inorganicpigment) having a minimum visible reflectance in a visible region at awavelength of from 400 to 780 nm of at least 40%.[5] The optical layer according to [4], wherein the light scatteringinorganic pigment has a refractive index of from 1.50 to 2.60.[6] The optical layer according to [4] or [5], wherein the lightscattering inorganic pigment is an organic pigment having an averageparticle size of from 10.0 to 2,000 nm and a specific surface area offrom 2.0 to 1,000 m²/g.[7] The optical layer according to any one of [1] to [6], wherein thematrix is at least one member selected from a fluororesin, a siliconeresin, and a sintered product obtained by sintering a glass fritcomposition.[8] The optical layer according to any one of [1] to [7], which has anaverage near infrared transmittance of from 10 to 100%, which is a valuecalculated by simply averaging near infrared transmittances at 5 nmintervals in a near infrared region at a wavelength of from 780 to 1,500nm.[9] The optical layer according to any one of [1] to [8], which furtherhas a substrate layer, and has the functional layer laminated on atleast one surface of the substrate layer.[10] A method for producing an optical layer, which comprises applying,to at least one surface of a substrate layer, a functional layer-formingcomposition at least containing an inorganic pigment having a maximumnear infrared reflectance in a near infrared region at a wavelength offrom 780 to 1,500 nm of at least 50%, an average particle size of from5.0 to 280.0 nm and a specific surface area of from 5.0 to 1,000 m²/g,and at least one member selected from a fluorinated polymer, a silanecompound and a glass frit composition, to form a functional layerthereby to form an optical layer comprising the substrate layer and thefunctional layer disposed on at least one surface of the substratelayer.[11] An optical layer-provided solar cell module, comprising solar cellsand the optical layer as defined in any one of [1] to [9], wherein theoptical layer is disposed on the side of plane of incidence of sunlightof the solar cells.[12] The solar cell module according to [11], wherein the solar cellsare CIS solar cells or CIGS solar cells.[13] An outer wall material for building, comprising the opticallayer-provided solar cell module as defined in [11] or [12].[14] A building comprising a solar cell module, and the optical layer asdefined in any one of [1] to [9], disposed on the side of plane ofincidence of sunlight of the solar cell module.[15] An optical layer, which comprises a functional layer containing aninorganic pigment and a matrix in which the inorganic pigment isdispersed, and a substrate layer comprising a glass plate, and has thefunctional layer laminated on at least one surface of the substratelayer, wherein at least a part of the inorganic pigment is an inorganicpigment having a maximum near infrared reflectance in a near infraredregion at a wavelength of from 780 to 1,500 nm of at least 50%, anaverage particle size of from 5.0 to 280.0 nm and a specific surfacearea of from 5.0 to 1,000 m²/g.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a coloredoptical layer capable of forming a solar cell module excellent in thedesign, and the power generation efficiency and the weather resistance,a method for producing an optical layer, an optical layer-provided solarcell module, an outer wall material for building, and a building.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating an exampleof an optical layer of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating anembodiment of an optical layer-provided solar cell module of the presentinvention.

FIG. 3 is a graph illustrating a sunlight spectrum on the ground and aspectral sensitivity curve of a monocrystalline silicon solar cell.

FIG. 4 is a cross-sectional schematically illustrating an embodiment ofan optical layer-provided solar cell module of the present invention.

FIG. 5 is a cross-sectional schematically illustrating an embodiment ofan optical layer-provided solar cell module of the present invention.

FIG. 6 is a plan view schematically illustrating an example of a solarcell array constituted by optical layer-provided solar cell modules ofthe present invention.

DESCRIPTION OF EMBODIMENTS

Meanings of terms in the present invention are as follows.

A colored inorganic pigment means an inorganic pigment having anabsorption peak in a visible region at a wavelength of from 400 to 780nm. A white inorganic pigment means an inorganic pigment having noabsorption peak in a visible region at a wavelength of from 400 to 780nm.

The average particle size of an inorganic pigment means a volume-basedcumulative 50% diameter (D50) obtained by measurement with respect tothe inorganic pigment subjected to ultrasonic treatment, by using aparticle size distribution measuring apparatus, and detailed measurementconditions are as described in Examples. In Examples, as the particlesize distribution measuring apparatus, Nanotrac Wave II-EX150(manufactured by MicrotracBEL Corp.) was used.

The specific surface area of an inorganic pigment is a value obtained bynitrogen adsorption BET method at 200° C. for 20 minutes under deaeratedconditions, using a specific surface area measuring apparatus. InExamples, as the specific surface area measuring apparatus, HMmodel-1208 (manufactured by Mountech Co., Ltd.) was used.

The density of an inorganic pigment is a value obtained by measurementby a pycnometer. In Examples, ULTRAPYC 1200e (manufactured byQuantachrome) was used.

The composition of an inorganic pigment is suitably analyzed e.g. byfluorescent X-ray analysis, ICP atomic emission spectroscopy, or atomicabsorption analysis.

The L* value, the a* value and the b* value of an inorganic pigment arevalues calculated from a diffuse reflectance spectrum obtained bymeasurement by diffuse reflectance method in accordance with JISZ8781-4: 2013, and a detailed measurement method is as described inExamples.

The maximum near infrared reflectance and the minimum visiblereflectance of an inorganic pigment are a maximum reflectance at awavelength of from 780 to 1,500 nm and a minimum reflectance at awavelength of from 400 to 780 nm, respectively, calculated from adiffuse reflectance spectrum obtained by measurement by diffusereflectance method.

The thickness of each layer of an optical layer is suitably obtainede.g. by a thickness meter or an eddy-current instrument for measuringthickness.

The average visible transmittance and the average linear visibletransmittance of an optical layer are values calculated by simplyaveraging visible transmittances at 5 nm intervals in a visible regionat a wavelength of from 400 to 780 nm by using a spectrophotometer suchthat the optical layer is disposed so that light enters from the normaldirection of the surface of the optical layer.

The average near infrared transmittance of an optical layer is a valuecalculated by simply averaging near infrared transmittances at 5 nmintervals in a near infrared region at a wavelength of from 780 to 1,500nm by using a spectrophotometer such that the optical layer is disposedso that light enters from the normal direction of the surface of theoptical layer.

The L* value, the a* value and the b* value of an optical layer arevalues calculated from a reflectance spectrum obtained by measuring thereflected light at 5 nm intervals at a wavelength of from 200 to 1,500nm by using a spectrophotometer such that the optical layer is disposedso that light enters from the normal direction of the surface of theoptical layer, in accordance with JIS Z8781-4: 2013.

In Examples, as the spectrophotometer, U-4100 (manufactured by HitachiHigh-Technologies Corporation) was used.

A “(meth)acrylate” generally means an acrylate and a methacrylate, and“(meth)acrylic” generally means “acrylic” and “methacrylic”.

The hydrolyzable silyl group is a group to be converted to a silanolgroup by hydrolysis.

The acid value and the hydroxy value are values measured in accordancewith JIS K0070-3 (1992).

The mass of the solid content of e.g. a composition is a mass, in a casewhere the composition contains a solvent, having the solvent removedfrom the composition. The mass of the solid content of a composition isobtained as a mass remaining after the composition is heated at 130° C.for 20 minutes.

According to the optical layer of the present invention, a solar cellmodule excellent in the design, and the power generation efficiency andthe weather resistance, can be formed, which is estimated to be from thefollowing reasons.

The optical layer of the present invention comprises a functional layercontaining an inorganic pigment (hereinafter sometimes referred to as aspecific inorganic pigment) having a maximum near infrared reflectancein a near infrared region at a wavelength of from 780 to 1,500 nm of atleast 50%, an average particle size of from 5.0 to 280.0 nm and aspecific surface area of from 5.0 to 1,000 m²/g, whereby scattering ofnear infrared light in the optical layer is controlled, and nearinfrared light which is transmitted through the optical layer and canarrive at solar cells can be sufficiently secured. Accordingly, it isconsidered that of sunlight which entered the optical light, nearinfrared light is likely to selectively arrive at solar cells, and anoptical layer excellent in the design and the power generationefficiency can be obtained. Further, optional coloring is possible by acolored inorganic pigment as the specific inorganic pigment, whereby theoptical layer is excellent in the design and is excellent in the weatherresistance as well.

Now, an example of the optical layer of the present invention and theoptical layer-provided solar cell module of the present invention willbe described with reference to drawings. The optical layer of thepresent invention will sometime be referred to as the present opticallayer, and the optical layer-provided solar cell module of the presentinvention will sometimes be referred to as the present solar cellmodule.

FIG. 1 is a cross-sectional view schematically illustrating an exampleof the present optical layer.

As shown in FIG. 1, the present optical layer 10 comprises a substratelayer 110 and a functional layer 120.

The present optical layer is preferably a colored optical layercontaining the specific inorganic pigment, particularly preferably acolored optical layer containing a colored inorganic pigment as thespecific inorganic pigment. Hereinafter, the specific inorganic pigmentwhich is a colored inorganic pigment will sometimes be referred to as aspecific colored inorganic pigment. The specific colored inorganicpigment may be used in combination with a white specific inorganicpigment, or may be used in combination with a white pigment other thanthe specific inorganic pigment.

The present optical layer which is colored is colored since it containsthe specific colored inorganic pigment and contributes to the design ofthe present solar cell module. The present optical layer being coloredspecifically means an average visible transmittance being at most 90%.

The present optical layer preferably has, in view of the design, afunctional layer having in the L*a*b* color space an L* value of from 5to 100, an a* value of from −60 to 60 and a b* value of from −60 to 60,more preferably an L* value of from 15 to 80, an a* value of from 3 to30 and a b* value of from −60 to 60.

The present optical layer is, in order to achieve the desired color,particularly preferably a layer having the following combination of theL* value, the a* value and the b* value.

-   -   An optical layer having an L* value, an a* value and a b* value        of from 5 to 100, from −10 to 10 and from −15 to 10 in this        order (more preferably from 15 to 60, from 1.5 to 15 and from        −10 to 10 in this order).    -   An optical layer having an L* value, an a* value and a b* value        of from 25 to 70, from 0 to 30 and from −60 to −20 in this        order.    -   An optical layer having an L* value, an a* value and a b* value        of from 20 to 70, from 0 to 40 and from −20 to 30 in this order.    -   An optical layer having an L* value, an a* value and a b* value        of from 30 to 80, from −20 to 20 and from 0 to 60 in this order.

The present optical layer, which comprises the after-describedfunctional layer containing an inorganic pigment and a matrix, has abrighter color and achieves more excellent design of the present solarcell module, when the L* value, the a* value and the b* value are withinthe above combination.

The present optical layer has, in view of the power generationefficiency of the present solar cell module, an average near infraredtransmittance which is a value calculated by simply averaging nearinfrared transmittances at 5 nm intervals in a near infrared region at awavelength of from 780 to 1,500 nm, of preferably at least 10%, morepreferably at least 30%, further preferably at least 40%, particularlypreferably at least 60%. The average near infrared transmittance of thepresent optical layer is usually at most 100%.

The present optical layer has, in view of shielding properties of thepresent optical layer, an average visible transmittance which is a valuecalculated by simply averaging visible transmittances at 5 nm intervalsin a visible region at a wavelength of from 400 to 780 nm, of preferablyat most 80%, more preferably at most 50%, further preferably at most42.0%, particularly preferably at most 20%.

The average near infrared transmittance and the average visibletransmittance of the present optical layer may be adjusted, for example,e.g. by the type or the addition amount of the specific inorganicpigment or the after-described light scattering inorganic pigment, orthe thickness of the present optical layer.

The methods for measuring the near infrared transmittance and theaverage visible transmittance of the present optical layer are asdescribed above, and detailed measurement conditions are as described inthe after-described Examples.

The thickness of the present optical layer is, in view of handlingefficiency of the present solar cell module, preferably at least 10 μm,more preferably from 20 μm to 100 mm, particularly preferably from 100μm to 50 mm.

The functional layer in the present invention contains an inorganicpigment of which at least a part is a specific inorganic pigment, and amatrix in which the inorganic pigment is dispersed. The functional layermay contain at least one component other than the inorganic pigment andthe matrix.

Of the functional layer, the L* value, the a* value and the b* value andtheir preferred ranges are the same as those of the optical layer asdescribed above.

Of the functional layer, the average near infrared transmittance and theaverage visible transmittance and their preferred ranges are the same asthose of the optical layer as described above.

That is, in a case where the present optical layer has the functionallayer and a layer other than the functional layer, the layer other thanthe functional layer is preferably a layer which does not affect theaverage near infrared transmittance and the average visibletransmittance of the present optical layer. “Does not affect”specifically means that the difference in the average near infraredtransmittance and the difference in the average visible transmittancebetween an optical layer having no layer other than the functional layerand an optical layer having a layer other than the functional layer, arerespectively less than 10%, preferably less than 5%.

The functional layer has, in view of the weather resistance of thefunctional layer, a thickness of preferably from 1 to 1,000 μm, morepreferably from 10 to 1,000 μm, further preferably from 20 to 100 μm,particularly preferably from 25 to 60 μm.

The specific inorganic pigment in the present invention has a maximumnear infrared reflectance in a near infrared region at a wavelength offrom 780 to 1,500 nm of at least 50%, an average particle size of from5.0 to 280.0 nm, and a specific surface area of from 5.0 to 1,000 m²/g.

The maximum near infrared reflectance in a near infrared region at awavelength of from 780 to 1,500 nm of the specific inorganic pigment is,in view of the near infrared transmittance of the present optical layer,at least 50%, preferably at least 60%, more preferably at least 70%,particularly preferably at least 80%. The upper limit of the maximumnear infrared reflectance is usually 100%.

The maximum near infrared reflectance of the specific inorganic pigmentmay properly be adjusted by the type, composition and crystal structureof the inorganic pigment.

In the present invention, the specific colored inorganic pigment is usedto make the functional layer in the present invention be colored, andaccordingly an inorganic pigment which does not make the functionallayer be colored when used alone does not belong to the category of thecolored inorganic pigment. That is, a white inorganic pigment such assilicon oxide (particularly silicon dioxide) does not fall into thecategory of the colored inorganic pigment. Further, the functional layerbeing colored means that the functional layer having an average visibletransmittance of at most 90%.

The average particle size of the specific inorganic pigment is at least5.0 nm, preferably at least 50.0 nm, particularly preferably at least100.0 nm. The average particle size of the inorganic pigment is at most280.0 nm, preferably at most 200.0 nm, more preferably at most 180.0 nm,further preferably at most 160.0 nm, particularly preferably at most140.0 nm.

When the average particle size of the specific inorganic pigment is atmost 280.0 nm, the present optical layer has a high near infraredtransmittance, and the present solar cell module is excellent in thepower generation efficiency. When the average particle size of thespecific inorganic pigment is at least 1.0 nm, the present optical layeris excellent in shielding properties, and the present solar cell moduleis excellent in the design.

The specific surface area of the specific inorganic pigment is at least5.0 m²/g, preferably at least 10.0 m²/g, more preferably at least 15.0m²/g, particularly preferably at least 40.0 m²/g. The specific surfacearea of the inorganic pigment is at most 1,000 m²/g, preferably at most500 m²/g, particularly preferably at most 60.0 m²/g.

When the specific surface area of the specific inorganic pigment is atleast 5.0 m²/g and at most 1,000 m²/g, scattering of near infrared lightby the inorganic pigment is favorable, and the present solar cell moduleis excellent in the power generation efficiency.

Of the specific inorganic pigment, a particularly preferred combinationof the maximum near infrared reflectance, the average particle size andthe specific surface area is as follows.

-   -   An inorganic pigment having a maximum near infrared reflectance        of at least 60%, an average particle size of from 50.0 to 200.0        nm and a specific surface area of from 10.0 to 500 m²/g.    -   An inorganic pigment having a maximum near infrared reflectance        of at least 70%, an average particle size of from 100.0 to 180.0        nm and a specific surface area of from 15.0 to 60 m²/g.

The particle shape of the specific inorganic pigment is not particularlylimited. The specific inorganic pigment may have any particle shape, forexample, spherical, elliptic, needle, plate, rod, conical, columnar,cubical, cuboidal, diamond, star, scaly or irregular shape. Further, thespecific inorganic pigment may be hollow particles or may be solidparticles. Further, the specific inorganic pigment may be porousparticles.

The specific inorganic pigment is preferably spherical in view ofdispersibility.

The specific inorganic pigment is, in view of the design and the weatherresistance of the present optical layer, preferably composed of e.g. ametal oxide or a hydrate of a metal oxide, particularly preferably ametal composite oxide containing at least two types of metal elements.

The metal element may, for example, be Li, Na, Mg, K, Ca, Al, Si, Ti, V,Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, In, Sn, Sb, Ba, Ta,W, Pb, Bi, La or Ce. The metal element is, in view of the near infraredreflectance of the specific inorganic pigment, and the color tone andthe power generation efficiency of the present optical layer, preferablyAl, Fe, Co, Zn, Zr, Mn, Cr, Ce, Bi, Ni, Cu or Cd, more preferably Al,Fe, Co, Zr, Ce, Mn, Bi or Cu, further preferably Al, Fe, Co, Zn or Zr,particularly preferably Al, Fe or Co.

With a view to suppressing deterioration by the photocatalytic action, apart of or the entire metal oxide or its hydrate constituting thespecific inorganic pigment may further be surface-treated with the sameor different type of metal oxide or its hydrate (such as silicon oxideor aluminum oxide).

The specific inorganic pigment may be composed solely of the metal oxideor may contain other component. The component other than the metal oxidemay, for example, be an organic compound. The specific inorganicpigment, in view of the weather resistance of the present optical layer,preferably contains no other component or contains other component in aproportion of at most 50 mass % to the total mass of the inorganicpigment.

The specific inorganic pigment containing other component may be aninorganic pigment having a part of or the entire particles of the metaloxide surface-treated with e.g. an organic compound.

The specific colored inorganic pigment may, for example, be specificallya Co—Ni—Ti—Zn composite oxide, a Co—Li composite oxide, a Co—Alcomposite oxide, a Ti—Sb—Ni composite oxide, a Co—Zn—Si composite oxide,a Co—Al—Cr composite oxide, a Co—Al—Cr—Zn composite oxide, a Co—Cr—Zn—Ticomposite oxide, a Ti—Fe—Zn composite oxide, a Fe—Zn composite oxide, aFe—Cr composite oxide, a Mn—Bi composite oxide, a Cu—Bi composite oxide,a Cu—Fe—Mn composite oxide, an iron oxide or a hydrate of an iron oxide.The specific colored inorganic pigment is, in view of the dispersibilityand the near infrared reflectance of the inorganic pigment, and theshielding properties and the near infrared transmittance of the presentoptical layer, preferably a Co—Li composite oxide, a Co—Al compositeoxide, a Co—Al—Cr composite oxide, a Fe—Cr composite oxide, a Mn—Bicomposite oxide, a Cu—Bi composite oxide, a Cu—Fe—Mn composite oxide, aniron oxide or a hydrate of an iron oxide, more preferably a Co—Alcomposite oxide or an iron oxide, particularly preferably a Co—Alcomposite oxide or an iron oxide.

As the specific colored inorganic pigment, commercial products may beused, such as “Daipyroxide™” series (manufactured by Dainichiseika Color& Chemicals Mfg Co., Ltd.), “Cappoxyt” series (manufactured byCappelle), “Sicotrans” series (manufactured by BASF) and “Blue CR4”(manufactured by ASAHI KASEI KOGYO CO., LTD.

The colored inorganic pigment which is white may, for example, bespecifically titanium oxide, zirconium oxide, vanadium oxide, zincoxide, indium oxide, tin oxide, silicon oxide or aluminum oxide, and inview of the shielding properties of the present optical layer and thepower generation efficiency of the present solar cell module, it ispreferably titanium oxide, zirconium oxide or zinc oxide, particularlypreferably zirconium oxide.

With a view to suppressing deterioration by photocatalytic action, apart of or the entire metal oxide constituting the specific inorganicpigment which is white may further be surface-treated with the same ordifferent type of metal oxide (such as silicon oxide or aluminum oxide).

In a case where the weather resistance of the present optical layer isto be more improved, for the purpose of preventing deterioration byphotocatalytic action, the specific inorganic pigment preferablycontains no titanium oxide or contains titanium oxide in a proportion ofless than 1 mass % in the entire inorganic pigment.

As the specific inorganic pigment which is white, commercial productsmay be used, such as “TTO” series (manufactured by Ishihara SangyoKaisha, Ltd.), “MT” series (manufactured by TAYCA CORPORATION), “FINEX”series (manufactured by SAKAI CHEMICAL INDUSTRY CO., LTD.), XZ-F series(manufactured by SAKAI CHEMICAL INDUSTRY CO., LTD.) and “ZIRCOSTAR”series (manufactured by NIPPON SHOKUBAI CO., LTD.).

The specific colored inorganic pigment has, in view of the design of thepresent optical layer, in the L*a*b* color space an L* value of from 5to 100, an a* value of from −60 to 60 and a b* value of from −60 to 60,more preferably an L* value of from 15 to 80, an a* value of from 0.0 to3.0 and a b* value of from −60 to 60.

The specific colored inorganic pigment, in order that the presentoptical layer has a desired color, the following combination of the L*value, the a* value and the b* value.

-   -   An inorganic pigment having an L* value, an a* value and a b*        value of from 30 to 70, from 0.0 to 30 and from −60 to −20 in        this order.    -   An inorganic pigment having an L* value, an a* value and a b*        value of from 20 to 70, from 0.0 to 40 and from −20 to 30 in        this order.    -   An inorganic pigment having an L* value, an a* value and a b*        value of from 30 to 80, from −20 to 20 and from 0 to 60 in this        order.    -   An inorganic pigment having an L* value, an a* value and a b*        value of from 80 to 100, from −10 to 10 and from −10 to 10 in        this order.    -   An inorganic pigment having an L* value, an a* value and a b*        value of from 5 to 50, from −10 to 10 and from −10 to 10 in this        order.

The L* value, the a* value and the b* value of the inorganic pigment maybe adjusted e.g. by the composition of the above-described specificcolored inorganic pigment.

The density of the specific colored inorganic pigment is, in view of thedispersibility of the inorganic pigment, preferably from 2.0 to 10.0g/cm³, particularly preferably from 3.0 to 5.0 g/cm³.

The density of the specific inorganic pigment which is white is, in viewof the dispersibility of the inorganic pigment, preferably from 0.10 to10.0 g/cm³, particularly preferably from 5.0 to 7.0 g/cm³.

The refractive index of the specific inorganic pigment is, in order thatthe functional layer more selectively transmits near infrared light,preferably at most 4.00, more preferably at least 1.50 and at most 3.00,further preferably at least 1.90 and at most 2.60, particularlypreferably at least 2.10 and at most 2.40.

The refractive index of the specific inorganic pigment which is whiteis, in order that the functional layer more selectively transmits nearinfrared light, preferably at most 4.00, more preferably from 1.50 to3.00, further preferably from 1.90 to 2.60, particularly preferably from2.10 to 2.40.

The refractive index of an inorganic pigment means a refractive index ofthe material constituting the inorganic pigment (for example, in a casewhere the inorganic pigment is obtained by pulverizing the material, thematerial before pulverizing), and is usually a value regarding the abovematerial disclosed in literature.

The minimum visible reflectance and the refractive index of theinorganic pigment may be properly adjusted by the composition, crystalstructure, average particle size and specific surface area of theinorganic pigment.

The content of the specific inorganic pigment to the total mass of thefunctional layer is, in view of the design of the present optical layer,preferably at least 5 mass %, more preferably at least 10 mass %,particularly preferably at least 20 mass %. The content of the specificinorganic pigment to the total mass of the functional layer is, in viewof the near infrared transmittance of the present optical layer,preferably at most 80 mass %, more preferably at most 60 mass %,particularly preferably at most 50 mass %.

The proportion of the specific inorganic pigment to the total mass ofthe inorganic pigment contained in the functional layer is, in view ofthe design and the power generation efficiency, preferably at least 80mass %, particularly preferably at least 90 mass %.

The functional layer may contain two or more types of specific inorganicpigment. In a case where the specific colored inorganic pigment and thespecific inorganic pigment which is white are used in combination, theproportion of the specific inorganic pigment which is white to the totalamount of such specific inorganic pigments is preferably from 5 to 200mass %, more preferably from 20 to 150 mass %, particularly preferablyfrom 20 to 40 mass %. When the functional layer contains the specificcolored inorganic pigment in a larger amount than the specific inorganicpigment which is white, the shielding properties of the present opticallayer and the design of the present solar cell module will be wellbalanced.

Particularly, the specific inorganic pigment which is white is also alight scattering inorganic pigment having a minimum visible reflectancein a visible region at a wavelength of from 400 to 780 nm of at least40%. Accordingly, by mixing the specific colored inorganic pigment andthe specific inorganic pigment which is white, the present solar cellmodule is more excellent in shielding properties.

The specific inorganic pigment which is white has, in order that thefunctional layer more selectively scatters visible light, a minimumvisible reflectance in a visible region at a wavelength of from 400 to780 nm of at least 40%, preferably at least 80%, more preferably atleast 90%, particularly preferably at least 95%. The upper limit of theminimum visible reflectance is usually 100%.

The specific inorganic pigment in the present invention hardly scattersnear infrared light in sunlight. And, it is likely to improve the designsince it has sufficient absorption in a visible region. Further, it isexcellent in the weather resistance as compared with the organic pigmentand has the above average particle size and specific surface area and isthereby likely to be suitably dispersed in the functional layer.Accordingly, the present optical layer comprising the functional layercontaining the inorganic pigment in the present invention is consideredto have high shielding property and be excellent in the weatherresistance and further be excellent in the design and the powergeneration efficiency when applied to a solar cell module.

The functional layer may further contain, in view of the design of thepresent solar cell module, a light scattering inorganic pigment(excluding the specific inorganic pigment) having a minimum visiblereflectance in a visible region at a wavelength of from 400 to 780 nm ofat least 40%. Such a light scattering inorganic pigment other than thespecific inorganic pigment will hereinafter sometimes be referred to asa light scattering inorganic pigment.

Of the light scattering inorganic pigment, the minimum visualreflectance in a visible region at a wavelength of from 400 to 780 nm,the refractive index, the density, the shape and their preferred rangesare the same as those of the specific inorganic pigment which is whiteas described above. The light scattering inorganic pigment isconstituted by the same metal oxide or the like as the specificinorganic pigment which is white or flakey inorganic pigment having astructural color and is preferably a white inorganic pigment.

The average particle size of the light scattering inorganic pigment ispreferably at least 10.0 nm, more preferably at least 50.0 nm,particularly preferably at least 100.0 nm. The average particle size ofthe light scattering inorganic pigment is preferably at most 2,000 nm,more preferably at most 500.0 nm, particularly preferably at most 300.0nm.

When the average particle size of the light scattering inorganic pigmentis at most 2,000 nm, the present optical layer has a high near infraredtransmittance, and the present solar cell module is excellent in thepower generation efficiency. When the average particle size of the lightscattering inorganic pigment is at least 10 nm, it is excellent in thescattering of visible light.

The specific surface area of the light scattering inorganic pigment ispreferably at least 2.0 m²/g, particularly preferably at least 8.0 m²/g.The specific surface area of the light scattering inorganic pigment ispreferably at most 1,000 m²/g, particularly preferably at most 500 m²/g.

When the specific surface area of the light scattering inorganic pigmentis at most 1,000 m²/g, scattering of visible light increases, andaccordingly the present optical layer tends to have a high near infraredtransmittance. When the specific surface area of the light scatteringinorganic pigment is at least 2.0 m²/g, the present optical layer tendsto have a high near infrared transmittance.

The light scattering inorganic pigment may be a flaky inorganic pigment(pearl pigment) having a structural color in view of design of thepresent solar cell module.

The pearl pigment is a pigment comprising flaky particles (for example,particles having a maximum size of from 2 to 100 μm and a thickness offrom 0.01 to 10 μm) the surface of which is coated with a metal or itsoxide. The flaky particles may be composed of mica, sericite, talc,kaolin, smectite clay mineral, mica, sericite, plate-like titaniumdioxide, plate-like silica, plate-like aluminum oxide, boron nitride,barium sulfate, plate-like titania/silica composite oxide, glass or thelike. The metal or its oxide coating the surface of the flaky particlesmay be the metal or its oxide mentioned for the above inorganic pigment.The pearl pigment is preferably flaky particles comprising mica, glass,aluminum oxide or the like, the surface of which is covered withtitanium dioxide, iron oxide, silver or the like.

In a case where the functional layer contains the pearl pigment as thelight scattering inorganic pigment, it can achieve a brighter and moreglittering color tone, and the present solar cell module is moreexcellent in the design.

The pearl pigment may, for example, be METASHINE titania coated series(manufactured by Nippon Sheet Glass Co., Ltd.) or TWINCLEPEARL silvertype (manufactured by NIHON KOKEN KOGYO CO., LTD.).

In a case where the functional layer contains the light scatteringinorganic pigment, the content of the light scattering inorganic pigmentto the total mass of the functional layer is, in view of the nearinfrared transmittance of the functional layer, preferably from 1 to 90mass %, more preferably from 3 to 80 mass %, particularly preferablyfrom 5 to 60 mass %. In such a case, the present optical layer isparticularly excellent in the shielding properties and the near infraredtransmittance.

In a case where the functional layer contains a light scatteringinorganic pigment, the functional layer may contain two or more types oflight scattering inorganic pigment.

In a case where the functional layer contains the light scatteringinorganic pigment, the content of the light scattering inorganic pigmentis preferably at most 100 mass %, particularly preferably at most 10mass % to the total mass of the specific inorganic pigment contained inthe functional layer. In such a case, the shielding properties of thepresent optical layer and the design of the present solar cell modulewill be balanced.

In a case where the functional layer contains both the light scatteringinorganic pigment and the specific inorganic pigment, the total contentof the light scattering inorganic pigment and the specific inorganicpigment in the functional layer is preferably at least 5 mass % and atmost 80 mass %, particularly preferably at least 20 mass % and at most50 mass %, to the total mass of the functional layer. In such a case,the present optical layer is particularly excellent in the shieldingproperties and the near infrared transmittance.

The matrix in the present invention has a function to fix the inorganicpigment in a dispersed state. The component constituting the matrix may,for example, be a resin, glass obtained by sintering a glass fritcomposition, or silica. The matrix may be constituted by two or more ofthe above components.

The resin constituting the matrix may be a thermoplastic resin or acured product of a curable resin. A crosslinked product of a polymerhaving crosslinkable groups, a condensation polymerization product of acompound having condensation-polymerizable groups, anaddition-polymerized product of a compound having addition-polymerizablegroups and the like also fall into the category of the thermoplasticresin and the cured product of a curable resin. Further, a thermoplasticresin having reactive groups such as hydroxy groups may act as the resinconstituting the matrix without reaction of the reactive groups.

The thermoplastic resin or an uncured curable resin for forming theresin constituting the matrix properly contains components necessary forforming the matrix resin (for example, the after-described component Xsuch as a curing agent).

The resin forming the matrix may, for example, be an alkyd resin, anamino alkyd resin, a polyester resin, an epoxy resin, an urethane resin,an epoxy-polyester resin, a vinyl acetate resin, an acrylic resin, avinyl chloride resin, a phenol resin, a modified polyester resin, afluororesin, an acrylic silicone resin, a silicone resin, anethylene/vinyl acetate resin, or a polyvinyl butyral resin. Among them,the resin to be the resin constituting the matrix by curing orcrosslinking is a resin the cured product or crosslinked product ofwhich constitutes the matrix. The resin constituting the matrix is, inview of the weather resistance, preferably a fluororesin comprising afluorinated polymer or a crosslinked product of a crosslinkablefluorinated polymer, and in view of the heat resistance, preferably asilicone resin comprising a condensation polymerization product of acondensation-polymerizable silane compound.

The matrix may be constituted by two or more types of resin.

In a case where the matrix in the present invention contains afluororesin, the fluororesin to be used for forming the matrix containsa fluorinated polymer having units based on a fluoroolefin (hereinaftersometimes referred to as units F) and as the case requires, at least onecomponent X other than the fluorinated polymer described hereinafter.

A unit generally means an atomic group based on one monomer moleculedirectly formed by polymerization of the monomer, and an atomic groupobtained by chemical conversion of a part of the atomic group. Thecontent (mol %) of each units to all the units in a polymer is obtainedby analyzing the polymer by nuclear magnetic resonance (NMR)spectroscopy.

A fluoroolefin is an olefin having at least one hydrogen atomsubstituted by a fluorine atom. In the fluoroolefin, at least onehydrogen atom not substituted by a fluorine atom may be substituted by achlorine atom.

The fluoroolefin may, for example, be specifically CF₂═CF₂, CF₂═CFCl,CF₂═CHF, CH₂═CF₂, CF₂═CFCF₃, CF₂═CHCF₃, CF₃CH═CHF, CF₃CF═CH₂ or amonomer represented by CH₂═CX^(f0)(CF₂)_(n0)Y^(f0) (wherein X^(f0) andY^(f0) are each independently a hydrogen atom or a fluorine atom, and n0is an integer of from 2 to 10), and in view of excellent weatherresistance of the functional layer, preferably CF₂═CF₂, CH₂═CF₂,CF₂═CFCl, CF₃CH═CHF, CF₃CF═CH₂, particularly preferably CF₂═CFCl. Thefluoroolefin may be used in combination of two or more.

The fluorinated polymer may have only units F, may have units F andunits based on a monomer containing a fluorine atom other than thefluoroolefin, or may have units F and units based on a monomercontaining no fluorine atom.

The fluorinated polymer having only units F may, for example, be ahomopolymer of the fluoroolefin or a copolymer of at least two types offluoroolefin, specifically, polytetrafluoroethylene,polychlorotrifluoroethylene, a tetrafluoroethylene/hexafluoropropylenecopolymer or polyvinylidene fluoride.

The fluorinated polymer having units F and units based on a monomercontaining a fluorine atom other than the fluoroolefin may, for example,be a fluoroolefin/perfluoro(alkyl vinyl ether) copolymer, specifically,a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer.

The fluorinated polymer preferably has units F and units based on amonomer containing no fluorine atom, in view of the dispersibility ofthe inorganic pigment in the matrix.

The fluorinated polymer having units F and units based on a monomercontaining no fluorine atom may, for example, be achlorotrifluoroethylene/vinyl ether copolymer, achlorotrifluoroethylene/vinyl ether/vinyl ester copolymer, achlorotrifluoroethylene/vinyl ester/allyl ether copolymer, atetrafluoroethylene/vinyl ester copolymer, a tetrafluoroethylene/vinylester/allyl ether copolymer or an ethylene/tetrafluoroethylenecopolymer. It is preferably a chlorotrifluoroethylene/vinyl ethercopolymer, whereby the present solar cell module is excellent in thedesign.

The content of the units F is, in view of the weather resistance of thefunctional layer, preferably from 20 to 100 mol %, more preferably from30 to 70 mol %, particularly preferably from 40 to 60 mol %, to all theunits contained in the fluorinated polymer.

The fluorinated polymer preferably has, in view of the durability of thefunctional layer, as the units based on a monomer containing no fluorineatom, units having a crosslinkable group (hereinafter sometimes referredto as units (1)). The units (1) may be units based on a monomer having acrosslinkable group (hereinafter sometimes referred to as a monomer (1))or may be units obtained by converting crosslinkable groups of afluorinated polymer having units (1) to different crosslinkable groups.Such units may be units obtained by reacting a fluorinated polymerhaving units having a hydroxy group with a polycarboxylic acid or itsacid anhydride or the like to convert one or more or all of the hydroxygroups to carboxy groups. The crosslinkable group may be a hydroxygroup, a carboxy group, an amino group, an epoxy group or a hydrolyzablesilyl group, and is preferably a hydroxy group or a carboxy group inview of the strength of the functional layer.

The crosslinkable group which the unit (1) has may be crosslinked by theafter-described curing agent in the matrix formed, or may remain withoutbeing crosslinked, and is preferably crosslinked with the curing agent.When the crosslinkable group which the unit (1) has is crosslinked bythe curing agent, the functional layer is more excellent in durability.When the crosslinkable group which the unit (1) has remains withoutbeing crosslinked, the dispersibility of the inorganic pigment in thematrix is more excellent.

The monomer having a hydroxy group may, for example, be a vinyl ether, avinyl ester, an allyl ether, an allyl ester, a (meth)acrylic acid esteror allyl alcohol, having a hydroxy group.

The monomer (1) having a hydroxy group may, for example, be specificallyCH₂═CHO—CH₂—cycloC₆H₁₀—CH₂OH, CH₂═CHCH₂O—CH₂-cycloC₆H₁₀—CH₂OH,CH₂═CHO—CH₂-cycloC₆H₁₀—CH₂—(OCH₂CH₂)₁₅OH, CH₂═CHOCH₂CH₂OH,CH₂═CHCH₂OCH₂CH₂OH, CH₂═CHOCH₂CH₂CH₂CH₂OH or CH₂═CHCH₂OCH₂CH₂CH₂CH₂OH,and in view of copolymerizability with the fluoroolefin, preferablyCH₂═CHCH₂OCH₂CH₂OH or CH₂═CHOCH₂CH₂CH₂CH₂OH.

“-cycloC₆H₁₀—” represents a cyclohexylene group, and the bindingposition of “-cycloC₆H₁₀—” is usually 1,4-position.

The monomer having a carboxy group may, for example, be an unsaturatedcarboxylic acid, a (meth)acrylic acid, or a monomer obtained by reactingthe hydroxy group of the monomer having a hydroxy group with acarboxylic anhydride.

The monomer having a carboxyl group may, for example, be specificallyCH₂═CHCOOH, CH(CH₃)═CHCOOH, CH₂═C(CH₃)COOH, HOOCCH═CHCOOH, a monomerrepresented by CH₂═CH(CH₂)_(n11)COOH (wherein n11 is an integer of from1 to 10), a monomer represented by CH₂═CHO(CH₂)_(n12)OC(O)CH₂CH₂COOH(wherein n12 is an integer of from 1 to 10), and in view ofcopolymerizability with the fluoroolefin, preferably a monomerrepresented by CH₂═CH(CH₂)_(n11)COOH or a monomer represented byCH₂═CHO(CH₂)_(n12)OC(O)CH₂CH₂COOH.

The monomer (1) may be used in combination of two or more.

The content of the units (1) is preferably from 0.5 to 35 mol %, morepreferably from 3 to 25 mol %, further preferably from 5 to 25 mol %,particularly preferably from 5 to 20 mol %, to all the units containedin the fluorinated polymer.

The fluorinated polymer may further have, as the units based on amonomer containing no fluorine atom, units based on a monomer having nocrosslinkable group. The units based on a monomer having nocrosslinkable group may be units (hereinafter sometimes referred to asunits (2)) based on at least one monomer (hereinafter sometimes referredto as a monomer (2)) selected from the group consisting of an alkene, avinyl ether, a vinyl ester, an allyl ether, an allyl ester and a(meth)acrylic acid ester.

The monomer (2) may, for example, be specifically ethylene, propylene,1-butene, ethyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinylether, cyclohexyl vinyl ether, vinyl acetate, vinyl pivalate, vinylneononanoate (manufactured by HEXION, trade name “VeoVa 9”), vinylneodecanoate (manufactured by HEXION, trade name “VeoVa 10”), vinylbenzoate, vinyl tert-butylbenzoate, tert-butyl (meth)acrylate or benzyl(meth)acrylate.

The monomer (2) may be used in combination of two or more.

In a case where the fluorinated polymer contains the units (2), thecontent of the units (2) is preferably from 5 to 60 mol %, particularlypreferably from 10 to 50 mol % to all the units contained in thefluorinated polymer.

As the fluorinated polymer, commercial products may be used, specificexamples of which include “LUMIFLON” series (trade name by AGC Inc.),“Kynar” series (trade name by Arkema), “ZEFFLE” series (trade name byDAIKIN INDUSTRIES, LTD.), “Eterflon” series (trade name by EternalMaterials Co., Ltd.) and “Zendura” series (trade name by Honeywell).

The fluorinated polymer is produced by a known method. As a method forproducing the fluorinated polymer, solution polymerization, emulsionpolymerization or the like may be mentioned.

As the component other than the fluorinated polymer contained in thefluororesin, a polymerization stabilizer, a polymerization inhibitor, asurfactant or the like, which is optionally added at the time ofproduction or after production of the fluorinated polymer may bementioned.

In a case where the matrix in the present invention contains thefluororesin, the content of the fluororesin in the functional layer is,in view of the weather resistance of the functional layer, preferablyfrom 5 to 95 mass %, particularly preferably from 10 to 90 mass %, tothe total mass of the functional layer.

In a case where the matrix in the present invention contains thefluororesin, the content of the fluorinated polymer in the functionallayer is, in view of the weather resistance of the functional layer,preferably from 5 to 95 mass %, particularly preferably from 10 to 90mass %, to the total mass of the functional layer.

In a case where the matrix in the present invention contains thefluororesin, the fluorine atom content in the functional layer is, inview of the dispersibility of the inorganic pigment in the matrix,preferably at most 65 mass %, more preferably at most 50 mass %,particularly preferably at most 40 mass %, further preferably at most 25mass %, most preferably at most 20%. Further, the fluorine atom contentin the functional layer is, in view of the weather resistance of thefunctional layer, preferably at least 0.1 mass %, more preferably atleast 3 mass %, particularly preferably at least 5 mass %, furtherpreferably at least 10 mass % to the total mass of the functional layer.

In such a case, particularly when the fluorine atom content in thefunctional layer is preferably from 0.1 to 25 mass %, particularlypreferably from 5 to 20 mass %, the inorganic pigment is favorablydispersed in the functional layer, and the present optical layer has ahigh near infrared transmittance and a high visible reflectance, wherebythe present solar cell module is excellent in the design and the powergeneration efficiency.

The fluorine atom content in the functional layer means the content(mass %) of fluorine atoms to all the atoms constituting the functionallayer. The fluorine atom content in the functional layer is obtained bymeasurement by automatic quick furnace combustion ion chromatography(AQF-IC) under the following conditions.

<Analytical Conditions>

Automatic Quick Furnace Combustion Apparatus

-   -   Apparatus: manufactured by Mitsubishi Chemical Analytech Co.,        Ltd., automatic quick furnace combustion apparatus AQF-100    -   Combustion conditions: solid sample mode    -   Sample amount: 2 to 20 mg

Ion Chromatograph

-   -   Apparatus: manufactured by Thermo Fischer SCIENTIFIC    -   Column: lonpac AG11HC+lonpac AS11HC    -   Eluent: KOH 10 mN (0 to 9 min), 10 to 16 mN (9 to 11 min), 16 mN        (11 to 15 min), 16 to 61 mN (15 to 20 min), 60 mN (20 to 25 min)    -   Flow rate: 1.0 mL/min    -   Suppressor: ASRS    -   Detector: conductance detector    -   Amount injected: 5 μL

In a case where the matrix in the present invention is a silicone resin,the silicone resin contains a hydrolyzed condensate of a silane compoundand as the case requires, at least one component X other than thehydrolyzed condensate of a silane compound, described hereinafter.

The silane compound may, for example, be a chlorosilane, a silazane oran alkoxysilane, and in view of the reactivity of the silane compound,preferably an alkoxysilane.

The chlorosilane may, for example, be trichlorosilane or trimethylchlorosilane.

The silazane may, for example, be hexamethyl disilazane or heptamethyldisilazane.

The alkoxysilane has at least one alkoxy group directly bonded to thesilicon atom. The alkoxysilane may have at least one group directlybonded to the silicon atom, other than the alkoxy group. Further, thealkoxysilane may have a hydrogen atom.

As the alkoxysilane, in view of durability of the functional layer, itis preferred to use a tetraalkoxysilane having 4 alkoxy groups directlybonded to the silicon atom, and an alkoxysilane having from 1 to 3alkoxy groups directly bonded to the silicon atom, in combination.

As at least one group directly bonded to the silicon atom, other thanthe alkoxy group, a hydroxy group, an alkyl group, an aromatic alkylgroup, a vinyl group, an epoxy group, a styryl group, a (meth)acrylicgroup, an amino group, an isocyanate group, a mercapto group, a ureidogroup, a polyfluoropolyether group or a polyfluoroalkyl group, may, forexample, be mentioned, and in view of crack resistance of the siliconeresin, an alkyl group or an aromatic alkyl group is preferred.

The alkyl group may, for example, be a methyl group, an ethyl group, apropyl group, a hexyl group or an octyl group, and is preferably amethyl group, an ethyl group or a propyl group.

The aromatic alkyl group may, for example, be an aryl group or a phenylgroup, and is preferably a phenyl group.

As at least one group directly bonded to the silicon atom, other thanthe alkoxy group, in view of hardness of the functional layer, a methylgroup, an ethyl group, a propyl group or a phenyl group is preferred.

The alkoxysilane may, for example, be specifically tetramethoxysilane,tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane,methyltrimethoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane,phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-glycidoxypropyltrimethoxysilane,3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane,3-acryloyloxypropyltrimethoxysilane, perfluoropolyether triethoxysilaneor perfluoroethyl triethoxysilane, and is preferably tetraethoxysilane,methyltrimethoxysilane or phenyltriethoxysilane. The silane compound is,in view of crack resistance of the functional layer, preferably at leastone member selected from tetraethoxysilane, methyltrimethoxysilane andphenyltriethoxysilane.

As the silane compound, further a bis-silane may be used. The bis-silaneis a compound having a structure such that two silicon atoms having ahydrolyzable group are bonded via a bivalent linking group.

The bivalent linking group may be a bivalent hydrocarbon group such asan alkylene group, an alkenylene group or an arylene group. The bivalenthydrocarbon group may have at least one group selected from —O—, —S—,—CO— and —NR_(S1)— (wherein R_(S1) is a hydrogen atom or a monovalenthydrocarbon group) between carbon atoms. The bivalent linking group ispreferably a C₂₋₈ alkylene group, particularly preferably a C₂₋₆alkylene group.

The hydrolyzable group may, for example, be an alkoxy group, an acyloxygroup, a ketoxime group, an alkenyloxy group, an amino group, an aminoxygroup, an amide group, an isocyanate group or a halogen atom, and ispreferably an alkoxy group (particularly a methoxy group or an ethoxygroup), an isocyanate group or a halogen atom (particularly a chlorineatom).

To the silicon atom which the bis-silane has, in addition to thehydrolyzable group, a hydrogen atom, a hydroxy group, a monovalenthydrocarbon group or the like may be bonded. The monovalent hydrocarbongroup may, for example, be an alkyl group, an alkenyl group or an arylgroup. In the bis-silane, the number of the hydrolyzable group bonded toone silicon atom is preferably from 1 to 3, and in view of the reactionrate, preferably 2 or 3, particularly preferably 3.

The silane compound may be used in combination of two or more.

The hydrolyzed condensate of the silane compound is obtained by mixingat least one silane compound, followed by drying by heating in thepresence of water and as the case requires, the after-described catalyst(such as an acid catalyst or a basic catalyst).

In a case where the matrix in the present invention contains thesilicone resin, the carbon atom content in the functional layer is, inview of the heat resistance of the functional layer, preferably at most30 at %, particularly preferably at most 20 at %. The carbon atomcontent in the functional layer may be adjusted by the type and theamount of the silane compound.

The carbon atom content in the functional layer means the content (at %)of carbon atoms to all the atoms constituting the functional layer. Thecarbon atom content in the functional layer is obtained by an averagevalue by measuring the carbon element number proportion (at %) withrespect to optional three points on the surface of the functional layerat an accelerating voltage of 15 keV, and in Example, it is a valueobtained by analysis by SEM-EDX (“S-4300”, trade name, manufactured byHitachi Ltd. and “EMAX”, trade name, manufactured by HORIBA, Ltd.).

In a case where the matrix in the present invention is the siliconeresin, in view of the crack resistance of the functional layer and witha view to making the functional layer thick and improving the shieldingproperties of the functional layer, the functional layer preferablyfurther contains scaly silica particles.

“Scaly” in the scaly silica particles means a flat shape. The shape ofthe particles can be confirmed by a transmission electron microscope.

Scaly silica particles comprise, for example, flaky silica primaryparticles and silica secondary particles formed by a plurality of flakysilica primary particles aligned and overlaid so that their faces are inparallel with each other. The silica secondary particles usually have alaminated structure particle shape. The scaly silica particles maycomprise only either one of the silica primary particles and the silicasecondary particles.

The thickness of the silica primary particles is preferably from 0.001to 0.1 μm. When the thickness of the silica primary particles is withinthe above range, scaly silica secondary particles having a plurality ofsilica primary particles aligned and overlaid so that their faces are inparallel with each other can be formed. The average aspect ratio of thesilica primary particles is preferably at least 2, more preferably atleast 5, particularly preferably at least 10.

The thickness of the silica secondary particles is preferably from 0.001to 3 μm, particularly preferably from 0.005 to 2 μm. The average aspectratio to the thickness of the silica secondary particles is preferablyat least 2, more preferably at least 5, particularly preferably at least10. The silica secondary particles are preferably present independentlyof one another without being fused.

The thicknesses of the silica primary particles and the silica secondaryparticles are measured by an atomic force microscope.

The maximum lengths of the silica primary particles and the silicasecondary particles are measured by a transmission electron microscope.

The aspect ratio is the ratio (maximum length/thickness) of the maximumlength to the thickness of each particle.

The average aspect ratio is an average of aspect ratios of randomlyselected 50 particles.

The average maximum particle size of the scaly silica particles is, inview of excellent crack resistance even when the functional layer isthick, preferably at least 0.05 μm, particularly preferably at least0.10 μm. The average maximum particle size of the scaly silica particlesis, in view of the dispersibility in the matrix, preferably at most 3.00μm, particularly preferably at most 1.50 μm.

The average maximum particle size of the scaly silica particles is anaverage of maximum particle sizes of randomly selected 50 particlesmeasured by a transmission electron microscope.

In a case where the functional layer contains the scaly silicaparticles, the thickness of the functional layer is preferably at least1 μm, more preferably at least 3 μm, particularly preferably at least 10μm. The thickness of the functional layer in the above case ispreferably at most 300 μm, more preferably at most 150 μm, particularlypreferably at most 100 μm.

In a case where the functional layer contains the scaly silicaparticles, the ratio (thickness of functional layer/average maximumparticle size) of the thickness of the functional layer to the averagemaximum particle size of the scaly silica particles is preferably atleast 3, more preferably at least 10, particularly preferably at least20. The ratio is preferably at most 500, more preferably at most 400,particularly preferably at most 300.

In a case where the functional layer contains the scaly silicaparticles, the volume fraction of the scaly silica particles in thefunctional layer is preferably from 5 to 100%, particularly preferablyfrom 10 to 30%, with a view to adjusting the thickness of the functionallayer and in view of excellent crack resistance of the functional layer.

The volume fraction of the scaly silica particles in the functionallayer is determined as follows.

First, the cross-section of the functional layer in the thicknessdirection is observed by an SEM “S-4300”, trade name, manufactured byHitachi Ltd.), and with respect to the obtained image, an optional rangewith a width of 1.5 μm in a direction at right angles to the thicknessdirection is analyzed by an image analysis software attached to obtainarea fractions (percentages (%) based on the total area (thickness×1.5μm) of the cross-section analyzed being 100%) of the matrix, the scalysilica particles and the inorganic pigment.

Likewise, with respect to the cross-section SEM image of the functionallayer in the thickness direction, two other optional ranges with a widthof 1.5 μm are analyzed and the area fractions are obtained.

Finally, the area fractions with respect to totally three ranges with athickness of 1. 5 μm, are averaged to obtain the volume fraction of thescaly silica particles.

In a case where the functional layer contains the scaly silicaparticles, the content of the inorganic pigment in the functional layeris preferably at least 1 mass %, more preferably at least 3 mass %,particularly preferably at least 5 mass % to the total mass of thefunctional layer. The content of the inorganic pigment in the functionallayer is preferably at most 50 mass %, more preferably at most 40 mass%, particularly preferably at most 30 mass % to the total mass of thefunctional layer.

In a case where the functional layer contains the scaly silicaparticles, it is considered that when the ratio of the average maximumparticle size of the scaly silica particles to the thickness of thefunctional layer is at least 3 and at most 500, the scaly silicaparticles are likely to be aligned so that the surface directions of thescaly silica particles are in parallel to the direction of the principalplane of the functional layer, and the functional layer is excellent inthe crack resistance. Further, it is considered that when the volumefraction of the scaly silica particles in the functional layer is from 5to 100% and the content of the inorganic pigment in the functional layeris from 1 to 50 mass %, the inorganic pigment is suitably disposedbetween the scaly silica particles, whereby the dispersibility of theinorganic pigment of the functional layer is excellent, and the abovealignment of the scaly silica particles is also more excellent, and thefunctional layer has further improved crack resistance and design. Inaddition, it is considered that the inorganic pigment is uniformlydispersed in the functional layer, whereby the present optical layer isexcellent in the weather resistance and the present solar cell module isexcellent in the power generation efficiency.

As the scaly silica particles, commercial products or processed productsthereof may, for example, be used, or products produced may be used. Asthe scaly silica particles, a powder may be used, or particles dispersedin a dispersion medium may be used. As commercial products of the scalysilica particles, for example, SUNLOVELY (trade name) seriesmanufactured by AGC Si-Tech Co., Ltd. may be mentioned.

In a case where the resin forming the matrix contains theafter-described curing agent, the functional layer preferably contains aresin having a crosslinked structure formed by reaction of thecrosslinkable groups which the resin has and the curing agent, in viewof the hardness and the durability of the functional layer.

Further, in a case where the resin forming the matrix contains theafter-described curing agent, the present optical layer may have acrosslinked structure formed by reaction of at least two selected fromthe group consisting of the crosslinkable groups which the resincontained in the functional layer has, the curing agent, and thereactive groups which a layer other than the functional layer has. Insuch a case, the reactive groups which the layer other than thefunctional layer has have a function as crosslinkable groups.

The reactive group which the layer other than the functional layer hasmay, for example, be a silanol group in a case where the layer otherthan the functional layer is a substrate layer comprising a glass plate,or a hydrolyzable silyl group in case where the layer other than thefunctional layer is a layer surface-treated with e.g. a silane couplingagent.

For example, in case where the functional layer is formed on a substratelayer comprising a glass plate from a resin containing a curing agenthaving at least one member selected from a hydrolyzable silyl group anda silanol group, the hydrolyzable silyl group or the like in the curingagent (specifically, a silanol group formed by hydrolysis) and thesilanol group present on the surface of the glass plate are reacted toform a crosslinked structure. Accordingly, the adhesion of thefunctional layer to the substrate layer is more excellent. Further, insuch a case, when the substrate layer is a layer comprising a glassplate surface-treated with e.g. a silane coupling agent, the silanolgroup present on the surface of the glass plate, the hydrolyzable silylgroup or the like which the silane coupling agent has, and thehydrolyzable silyl group or the like in the curing agent, are reacted toform a crosslinked structure. Accordingly, the adhesion between thesubstrate layer and the functional layer improves, and the presentoptical layer is excellent in the durability.

In a case where the matrix in the present invention is a sinteredproduct obtained by sintering a glass frit composition, the glass fritcomposition comprises a glass powder obtained by pulverizing glass andas the case requires, contains at least one component G describedhereinafter.

The 50% particle diameter (D50) of the glass powder is preferably from1.0 to 10.0 μm, preferably from 3.0 to 8.0 μm.

The 90% particle diameter (D90) of the glass powder is preferably from5.0 to 30.0 μm, preferably from 8.0 to 16.0 μm. The 50% particlediameter (D50) and the 90% particle diameter (D90) are particlediameters corresponding to the cumulative amount 50% and 90% in aparticle diameter cumulative distribution (volume basis). The 50%particle diameter (D50) and the 90% particle diameter (D90) are measuredby a laser diffraction particle size distribution measuring apparatus.

The glass powder preferably contains at least one element selected fromLi, B, Na, Mg, Al, Si, K, Ca, Ti, Mn, Cu, Zn, Sr, Ag, Ba, Bi, Fe, Co,Ce, Nb, Ta, Sb, Cs, P, Zr, La and Sn, more preferably contains at leastone element selected from Ba, B, Al, Cu, Zn, Bi, Fe and Ce, particularlypreferably contains at least one element selected from Ba, B and Zn.

The composition and the contents of the respective elements of the glasspowder are properly adjusted so that the glass powder has a suitablesoftening point.

The amount of the glass powder contained in the glass frit compositionis properly adjusted together with the amount of the after-describedthermal expansion coefficient-adjusting agent so that the thermalexpansion coefficient of a sintered product obtained by sintering theglass frit composition is suitable.

The softening point of the glass powder is, in a case where the presentoptical layer has a substrate layer comprising a glass plate, and afunctional layer containing a glass frit sintered product is directlylaminated on at least one surface of the substrate layer, required to beless than the softening point of the substrate layer, so as to preventdeformation by softening of the substrate layer at the time ofsintering. Particularly in a case where soda lime silicate glass is usedas the substrate layer, the softening point of the glass powder ispreferably from 450 to 700° C., particularly preferably from 500 to 600°C.

The glass powder is not particularly limited and for example, with aview to reducing the environmental burden, preferably a glass powdercomprising glass containing no lead, particularly preferably a glasspowder comprising barium zinc borate glass. The barium zinc borate glassis, for example, as represented by mass % based on oxides of metalelements contained in the glass, preferably glass containing from 20 to50% of BaO, from 10 to 35% of B₂O₃ and from 5 to 25% of ZnO.Particularly in a case where the present optical layer has a substratelayer comprising a glass plate and has a functional layer containing asintered product formed from a glass frit composition directly laminatedon at least one surface of the substrate layer, in view of hardness ofthe present optical layer, the glass powder preferably contains, asrepresented by mass % based on oxides of metal elements contained in theglass, from 28 to 43% of BaO, from 13 to 28% of B₂O₃ and from 10 to 20%of ZnO.

The component G may, for example, be a thermal expansioncoefficient-adjusting agent, a release agent or a reducing agent. Thesintered product is produced by using a binder or an organic solvent notcontained in the glass frit sintered product, in addition to thecomponent G.

The binder is to fix the glass powder in the glass frit compositionbefore sintering the glass frit composition and is removed by heatingwhen the glass frit composition is sintered. Accordingly, the binder isnot contained in the glass frit sintered product.

In a case where the glass frit composition contains the binder and theorganic solvent, the glass frit composition is in a paste form and canthereby be easily applied. The binder is preferably an organic binder,such as ethyl cellulose, a polypropylene carbonate acrylic resin, astyrene resin, a phenol resin or a butyral resin, and is preferablyethyl cellulose in view of printing properties.

The organic solvent is to dissolve the binder and is selected dependingupon the type of the binder. The organic solvent is removed by heatingat the time of drying by heating and sintering the glass fritcomposition. Accordingly, the glass frit sintered product does notcontain the organic solvent.

The organic solvent may, for example, be 2,2,4-trimethylpentane-1,3-diolmonoisobutyrate, ethylene glycol mono-2-ethylhexyl ether, α-terpineol,butyl carbitol acetate or a phthalate, and in view of printingproperties, preferably 2,2,4-trimethylpentane-1,3-diol monoisobutyrateor ethylene glycol mono-2-ethylhexyl ether.

The thermal expansion coefficient-adjusting agent is to adjust thethermal expansion coefficient of the functional layer at leastcontaining the glass frit composition and the inorganic pigment. Thethermal expansion coefficient of the functional layer and the thermalexpansion coefficient of the substrate (e.g. glass plate) do not fiteach other, when the glass frit composition is sintered to obtain asintered product, the functional layer or the substrate may be warped orhave cracking. Accordingly, in order to prevent warpage or cracking atthe time of forming the functional layer, for example, in a case wherethe functional layer is formed on the substrate layer, it is preferredto adjust the thermal expansion coefficient of the functional layer tobe close to the thermal expansion coefficient of the substrate layer bythe thermal expansion coefficient-adjusting agent.

The thermal expansion coefficient-adjusting agent is preferably at leastone member selected from cordierite, aluminum titanate, alumina,mullite, silica, zinc oxide ceramic, β-eucryptite, β-spodumene,zirconium phosphate ceramic and β-quartz solid solution, more preferablya powder thereof.

In a case where the thermal expansion coefficient-adjusting agent is apowder, the 50% particle diameter (D50) of the thermal expansioncoefficient-adjusting agent is preferably from 1.0 to 10.0 μm,preferably from 1.5 to 5.0 μm. The 90% particle diameter (D90) of thethermal expansion coefficient-adjusting agent is preferably from 1.0 to10.0 μm, preferably from 3.0 to 8.0 μm. The type and the amount of thethermal expansion coefficient-adjusting agent are properly selected sothat the glass frit composition has a desired thermal expansioncoefficient.

For example, in a case where the soda lime silicate glass is used forthe substrate layer, preferred is a combination of the barium zincborate glass powder as the glass frit composition, cordierite as thethermal expansion coefficient-adjusting agent and Co—Al composite oxideas the inorganic pigment.

In the matrix, the contents of the glass frit sintered product, thethermal expansion coefficient-adjusting agent and the inorganic pigmentare respectively preferably from 50 to 85 mass %, from 10 to 30 mass %and from 1 to 20 mass % in this order to the total mass of the matrix,particularly preferably from 60 to 80 mass %, from 15 to 25 mass % andfrom 5 to 10 mass %.

In the above case, the adhesion between the substrate layer and thefunctional layer is favorable, and the present optical layer isexcellent in the strength. Further, since the inorganic pigment isfavorably dispersed in the matrix, the present solar cell module isexcellent in the design and the power generation efficiency.

The functional layer in the present invention according to an embodimentis a layer formed of a functional layer-forming composition (hereinafterreferred to as composition (1)) at least containing the polymer(particularly the fluorinated polymer) and the inorganic pigment. Thecomposition (1) may contain two or more types of polymer. Further, thecomposition (1) may contain two or more types of inorganic pigment.

As the polymer, a polymer contained in the resin constituting the matrixas described above may be mentioned, and a fluorinated polymer ispreferred.

The inorganic pigment in the composition (1) is the same as theabove-described inorganic pigment in the present invention, and itsdetails are omitted.

In a case where the composition (1) is a functional layer-formingcomposition (hereinafter referred to as composition (1F)) containing afluorinated polymer as the polymer, the fluorinated polymer in thecomposition (1F) preferably has the following physical properties.

In a case where the fluorinated polymer is a fluorinated polymer havingcarboxy groups, the acid value of the fluorinated polymer is, in view ofthe strength of the functional layer, preferably from 1 to 200 mgKOH/g,preferably from 1 to 150 mgKOH/g, more preferably from 3 to 100 mgKOH/g,particularly preferably from 5 to 50 mgKOH/g.

In a case where the fluorinated polymer is a fluorinated polymer havinghydroxy groups, the hydroxy value of the fluorinated polymer is, in viewof the strength of the functional layer, preferably from 1 to 200mgKOH/g, preferably from 1 to 150 mgKOH/g, more preferably from 3 to 100mgKOH/g, particularly preferably from 10 to 60 mgKOH/g.

The fluorinated polymer may have only one of the acid value and thehydroxy value, or may have both.

The fluorine atom content in the fluorinated polymer is, in view ofdispersibility of the inorganic pigment in the matrix, preferably atmost 70 mass %, more preferably at most 50 mass %, particularlypreferably at most 30 mass %, most preferably at most 28 mass %.Further, the fluorine atom content in the fluorinated polymer ispreferably at least 10 mass %, particularly preferably at least 15 mass%, in view of the weather resistance of the functional layer.

Particularly when the fluorine atom content in the fluorinated polymeris preferably from 15 to 30 mass %, particularly preferably from 15 to28 mass %, the inorganic pigment is favorably dispersed in thefunctional layer, and the present optical layer has a high near infraredtransmittance and a high visible transmittance, and accordingly thepresent solar cell module is excellent in the design and the powergeneration efficiency.

The fluorine atom content in the fluorinated polymer means a proportion(mass %) of fluorine atoms to all the atoms constituting the fluorinatedpolymer. The fluorine atom content is obtained by analyzing thefluorinated polymer by nuclear magnetic resonance (NMR) spectroscopy.

Except for the above, the fluorinated polymer is the same as thefluorinated polymer in the matrix as described above, and its detailsare omitted.

The content of the fluorinated polymer in the composition (1F) is, inview of dispersibility of the inorganic pigment in the composition (1F),preferably from 10 to 90 mass %, particularly preferably from 20 to 40mass % to the total mass of the composition (1F).

The content of the fluorinated polymer in the solid content of thecomposition (1F) is, in view of the dispersibility of the inorganicpigment in the composition (1F), preferably from 10 to 90 mass %,particularly preferably from 40 to 70 mass % to the total mass of thesolid content in the composition (1F).

The content of the inorganic pigment in the solid content in thecomposition (1F) is, in view of the dispersibility of the inorganicpigment in the composition (1F), preferably from 5 to 80 mass %,particularly preferably from 20 to 50 mass % to the total mass of thesolid content in the composition (1F).

The composition (1) may contain, in addition to the inorganic pigmentand the polymer, at least one component X which is a component otherthan the inorganic pigment and the polymer. Such a component X may, forexample, be a curing agent, a catalyst, a filler (e.g. an organic fillersuch as resin beads), an organic pigment (such as carbon black (black),copper phthalocyanine (blue, green) or perylene (red)), an organicphotostabilizer, an organic ultraviolet absorber, an inorganicultraviolet absorber, a delustering agent, a dispersing agent, ananti-foaming agent, a leveling agent, a surface modifier, a degassingagent, a bulking agent, a thermal stabilizer, a thickener, a surfactant,an antistatic agent, an anti-corrosive agent, a silane coupling agent, astain-proofing agent, a low contamination treatment agent, a plasticizeror an adhesive.

However, in view of the weather resistance of the functional layer, itis preferred that no organic pigment is contained, or if contained, itscontent is less than 1 mass % in the entire pigment.

The composition (1) may contain, as the case requires, a component whichis not contained in the functional layer. Such a component may, forexample, be a liquid medium. A liquid medium such as water or an organicsolvent is a component removed e.g. by evaporation at the time offorming the matrix, and in a case where the functional layer is formedby means of e.g. coating, it is contained in the composition (1).

The solid content concentration in the composition (1F) is preferablyadjusted to preferably from 10 to 90 mass %, more preferably from 40 to70 mass % to the total mass of the composition (1F) by the liquidmedium.

In a case where the composition (1) contains a curable resin or acrosslinkable polymer, it particularly preferably contains, among thecomponents X, a curing agent which constitutes a crosslinked structurein the above-described functional layer.

In a case where the polymer in the composition (1) has crosslinkablegroups, the functional layer can be cured by crosslinking thecrosslinkable groups of the polymer and the curing agent. In such acase, the functional layer has a crosslinked structure of the polymerand the curing agent.

Further, in a case where the curing agent in the composition (1)contains at least one member selected from the hydrolyzable silyl groupand the silanol group, it is considered that the curing agent, the glassplate containing silicon oxide as the substrate layer and as the caserequires, the polymer, are reacted to form a functional layer having acrosslinked structure of the curing agent and the glass plate and as thecase requires, the polymer.

In a case where the composition (1) contains the curing agent, thecontent of the curing agent is preferably at least 5 parts by mass andat most 200 parts by mass, particularly preferably at least 10 parts bymass and at most 150 parts by mass, per 100 parts by mass of the polymerin the composition (1).

In a case where the polymer has hydroxy groups, the curing agent ispreferably a compound having at least 2 isocyanate groups or blockedisocyanate groups in one molecule.

In a case where the polymer is a curing agent having carboxy groups, thecuring agent is preferably a compound having at least 2 epoxy groups,carbodiimide groups, oxazoline groups or β-hydroxyalkylamide groups inone molecule.

In a case where the polymer has both hydroxy groups and carboxy groups,as the curing agent, it is preferred to use a compound having at least 2isocyanate groups or blocked isocyanate groups in one molecule and acompound having at least 2 epoxy groups, carbodiimide groups, oxazolinegroups or β-hydroxyalkylamide groups in one molecule in combination.

Further, in a case where the present optical layer has a substrate layercomprising a glass plate, the curing agent is preferably a curing agenthaving at least one member selected from a hydrolyzable silyl group anda silanol group, whereby the adhesion between the functional layer andthe substrate layer will more improve.

The composition (1) preferably contains a dispersing agent in view ofthe dispersibility of the inorganic pigment. The dispersing agent may,for example, be a fatty amide, an ester salt of an acid polyimide, anacrylic resin, an oxidized polyolefin or a polymer compatible with theinorganic pigment. As the dispersing agent, commercial products may beused, such as “DISPARLON” series (trade name by Kusumoto Chemicals,Ltd.) and “DISPERBYK” series (trade name by BYK Japan KK).

The functional layer in the present invention according to an embodimentis a layer formed of a functional layer-forming composition (hereinafterreferred to as composition (2)) at least containing a silane compound,scaly silica particles and an inorganic pigment. The composition (2) maycontain at least two types of silane compound and scaly silicaparticles. Further, the composition (2) may contain at least two typesof inorganic pigment.

In the composition (2), the silane compound, the scaly silica particles,the inorganic pigment and their contents are the same as the silanecompound and the scaly silica particles described for the silicone resinin the present invention and the inorganic pigment in the presentinvention, and their details are omitted.

The composition (2) may contain a component other than the silanecompound, the scaly silica particles and the inorganic pigment, and assuch components, the above component X may be mentioned.

The composition (2) preferably contains, among the components X, acatalyst which promotes hydrolysis of the silane compound. Such acatalyst may, for example, be an acid catalyst or an alkali catalyst,and is preferably an acid catalyst, in view of long term stability afterhydrolytic condensation of the silane compound.

The acid catalyst may, for example, be an inorganic acid (such as nitricacid, sulfuric acid or hydrochloric acid) or an organic acid (such asformic acid, oxalic acid, monochloroacetic acid, dichloroacetic acid ortrichloroacetic acid).

The alkali catalyst may, for example, be ammonia, sodium hydroxide,potassium hydroxide or electrolytically reduced water having a pH offrom 10.5 to 12.

It is preferred that the composition (2) at least contains a medium(particularly a liquid medium) and that the silane compound, the scalysilica particles and the inorganic pigment are dispersed in the liquidmedium. The liquid medium may be water, an organic solvent or a mixturethereof, and at least water is preferably contained.

The total content of the silane compound and the scaly silica particlesin the composition (2) is, in view of the dispersibility in thecomposition (2), preferably from 1 to 99 mass %, particularly preferablyfrom 30 to 90 mass % to the total mass of the composition (2).

The content of the inorganic pigment in the composition (2) is, in viewof the dispersibility of the inorganic pigment in the composition (2),preferably from 0.01 to 50 mass %, particularly preferably from 1 to 30mass % to the total mass of the composition (2).

The functional layer in the present invention according to an embodimentis a layer formed of a functional layer-forming composition (hereinafterreferred to as composition (3)) at least containing a glass fritcomposition and an inorganic pigment.

The glass frit composition and the inorganic pigment in the composition(3) are the same as the glass frit composition in the present inventionand the inorganic pigment in the present invention, and their detailsare omitted.

The composition (3) may contain a component other than the glass fritcomposition and the inorganic pigment, and as such a component, theabove-described component G may be mentioned, and the composition (3)preferably contains, among the components G, a thermal expansioncoefficient-adjusting agent.

The composition (3) may contain a binder or an inorganic solvent, whichis a component not contained in the sintered product, as mentionedabove. In such a case, the composition (3) is in a paste form, andapplication of the composition (3) and formation of the functional layerare easy. Further, the inorganic pigment is suitably dispersed in thecomposition (3), and the present solar cell module is excellent in thedesign.

In a case where the functional layer is a layer formed of thecomposition (1), the functional layer may be produced by forming thecomposition (1) into a layer, or may be produced by applying thecomposition (1) to a layer other than the functional layer which thepresent optical layer has (for example, a substrate layer), followed bydrying by heating. The functional layer is, in view of thedispersibility of the inorganic pigment in the matrix, preferablyproduced by applying the composition (1) to a layer other than thefunctional layer which the present optical layer has. That is, thecomposition (1) is preferably a coating material containing thefluorinated polymer.

In a case where the present solar cell module is to be produced, it ispreferred that the coating material is applied to a substrate layer toproduce an optical layer, which is contact-bonded to the after-describedencapsulant layer. Accordingly, the functional layer in the opticallayer is preferably a layer formed by applying the coating material,also in that the functional layer will not protrude at the edges at thetime of contact-bonding to the encapsulant layer, as compared with acase where the functional layer is a film.

In a case where the composition (1) is formed to produce the functionallayer, the forming method may, for example, be extrusion, injectionmolding or blow molding. In such a case, the composition (1) may beformed into a layer and laminated on a layer other than the functionallayer which the present optical layer has.

In a case where the composition (1) is a coating material (such as anaqueous coating material or a solvent-based coating material) containinga liquid medium and having the solid content of the composition (1)dispersed or dissolved in the medium, the coating method may, forexample, be specifically spray coating method, squeeze coating method,flow coating method, bar coating method, spin coating method, dipcoating method, screen printing method, gravure coating method, diecoating method, ink jet method, curtain coating method or a method usinga brush or a spatula. The composition (1) is preferably a solvent-basedcoating material in which the fluorinated polymer is dissolved ordispersed in a solvent, whereby a functional layer with favorabledispersibility in the matrix, can be formed.

In a case where the composition (1) is a coating material (e.g. a powdercoating material) containing no liquid medium, the coating method may,for example, be specifically electrostatic coating method, electrostaticspraying method, electrostatic dipping method, atomizing method,fluidized-bed coating method, spray coating method, spraying method,thermal spraying method or plasma spray coating method.

In a case where the composition (1) is applied to a layer other than thefunctional layer which the present optical layer has to produce thefunctional layer, the coating layer obtained by applying the composition(1) is preferably dried by heating, after applying. The temperature fordrying by heating the coating layer is usually from 0° C. to 300° C.,and the time for drying by heating is usually from 1 minute to 2 weeks.

In a case where the functional layer is a layer formed of thecomposition (1), the present optical layer is preferably a layercomprising a substrate layer and a functional layer directly laminatedon at least one surface of the substrate layer, wherein the substratelayer comprises a surface-treated glass plate. That is, in the abovecase, it is preferred that at least one surface of the glass plate issurface-treated by a known surface treatment method to obtain asubstrate layer, and on at least one surface of the obtained substratelayer, the composition (1) is directly applied to form a functionallayer thereby to obtain the present optical layer. Particularly in acase where the surface treatment is e.g. application of a silanecoupling agent, a —Si—OH group which the glass plate has in thesubstrate layer and a —Si—OH group which the silane coupling agent hasinteract with each other, and the surface-treated substrate layer andthe functional layer are closely contacted with each other, whereby thepresent optical layer is excellent in durability.

In a case where the functional layer is a layer formed of thecomposition (2), the functional layer is preferably produced by applyingthe composition (2) to a layer other than the functional layer which thepresent optical layer has (for example, a substrate layer), followed bydrying by heating. In such a case, the coating method may be the coatingmethod as described for the composition (1), and is preferably spraycoating method.

In a case where the composition (2) is applied by spray coating method,it can be applied, for example, by electrifying the composition (2) byusing a known electrostatic coating apparatus having a knownelectrostatic coating gun provided with a rotary atomizing head, andspraying it on a principal plane of the substrate layer (preferably asubstrate layer comprising a glass plate). After applying, it ispreferred to dry by heating a coating layer obtained by applying thecomposition (2) for curing thereby to form the functional layer. Bydrying the coating layer by heating, a hydrolyzed condensate of a silanecompound e.g. having a siloxane bond is formed. The temperature fordrying by heating the coating layer is usually from 30° C. to 700° C.,and the time for drying by heating is usually from 1 minute to 30minutes.

In a case where the functional layer is a layer formed of thecomposition (2), the present optical layer preferably has a glass plateand a functional layer directly laminated on at least one surface of theglass plate. That is, in the above case, the present optical layer ispreferably obtained by directly applying the composition (2) on at leastone surface of the substrate layer comprising a glass plate to form thefunctional layer. In such a case, it is considered that a —Si—OH groupwhich the glass plate has and a —Si—OH group which the silane compoundhas interact with each other and a part thereof form a Si—O—Si bond, andaccordingly the adhesion between the substrate layer and the functionallayer is particularly excellent, and the present optical layer isexcellent in durability.

In a case where the functional layer is a layer formed of thecomposition (3), the functional layer may be produced by applying thecomposition (3) on a layer other than the functional layer which thepresent optical layer has (for example, a substrate layer), followed bydrying by heating and sintering, or it may be produced by applying thecomposition (3) on e.g. a resin film, followed by drying by heating,removing the resin film or the like, and sintering the obtainedheat-dried product.

The coating method may be the coating method described for thecomposition (1), and is preferably curtain coating method, screenprinting method or ink jet method.

In a case where the composition (3) contains a binder and an organicsolvent, the organic solvent is removed by first drying by heating, thebinder is removed by second drying by heating, and sintering occurs inthird drying by heating, whereby the glass powder is bonded which thecomposition (3) contains.

The temperature for first drying by heating is preferably from 100 to150° C. The temperature for second drying by heating is preferably from300 to 450° C., particularly preferably from 350 to 400° C. Thetemperature for third drying by heating is preferably from 450 to 700°C., particularly preferably from 550 to 650° C. The temperature fordrying by heating and sintering may be properly adjusted e.g. by thetype of the substrate layer, the softening point of the glass fritcomposition, or the thermal expansion coefficient.

The substrate layer is made from a material which does not lower thenear infrared transmittance of the present optical layer. The substratelayer specifically has, an average near infrared transmittance of atleast 10%, preferably at least 100%, which is a value calculated bysimply averaging near infrared transmittances at 5 nm intervals in anear infrared region at a wavelength of from 780 to 1,500 nm.

The substrate layer is made of an organic material or an inorganicmaterial, and in view of the near infrared transmittance, it ispreferably a glass plate or a resin formed product, particularlypreferably a glass plate.

The glass plate may be made of e.g. soda lime silicate glass, quartzglass, crystal glass, alkali-free glass, aluminosilicate glass,borosilicate glass or barium borosilicate glass, and in view of highnear infrared transmittance, preferably made of soda lime silicateglass.

The soda lime silicate glass may, for example, be specifically glasshaving a composition comprising, as calculated as oxides, from 60 to 75mass % of SiO₂, from 0 to 3 mass % of Al₂O₃, more than 0 and at most 15mass % of CaO, from 0 to 12 mass % of MgO and from 5 to 20 mass % ofNa₂O. Here, SiO₂ is the main component of the soda lime silicate glass.

Soda lime silicate glass may further contain, in addition to the abovecomponents, at least one material selected from the group consisting ofK₂O, TiO₂, ZrO₂ and LiO₂.

Further, the soda lime silicate glass may further contain a clarifyingagent (such as SO₃, SnO₂ or Sb₂O₃).

The glass plate may be a tempered glass plate having tempering treatmentapplied thereto. A tempered glass plate is preferred since it is hardlybroken as compared with a glass plate having no tempering treatmentapplied thereto. As a tempered glass plate, for example, a glass platehaving a front layer having residual compressive stress, a rear layerhaving residual compressive stress, and an interlayer having residualtensile stress formed between the front layer and the rear layer, isused.

The tempering treatment may, for example, be specifically chemicaltempering treatment carried out e.g. by known ion exchange method orphysical tempering treatment carried out e.g. by known air-coolingtempering method. A chemically tempered glass plate has sufficientstrength even if the glass plate has a small plate thickness, since thefront layer or the rear layer has large residual compressive stress.

The resin formed product is a resin formed into e.g. a plate or a film.The resin may, for example, be a fluororesin, an alkyd resin, an aminoalkyd resin, a polyester resin, an epoxy resin, a urethane resin, anepoxy polyester resin, a vinyl acetate resin, a (meth)acrylic resin, avinyl chloride resin, a phenol resin, a modified polyester resin, anacrylic silicone resin or a silicone resin. The resin formed product ispreferably a fluororesin film in view of the weather resistance and thenear infrared transmittance.

The fluororesin may be a resin containing polytetrafluoroethylene,polychlorotrifluoroethylene, a tetrafluoroethylene/hexafluoropropylenecopolymer, polyvinylidene fluoride, a fluoroolefin/perfluoro(alkyl vinylether) copolymer or an ethylene/tetrafluoroethylene copolymer. Thefluororesin is, in view of processability and near infraredtransmittance, preferably a resin containing polyvinylidene fluoride oran ethylene/tetrafluoroethylene copolymer.

As the fluororesin, commercial products may be used, such as “Fluon”series (trade name by AGC Inc.) and “Kynar” series (trade name byArkema).

The average thickness of the substrate layer is optionally set dependingupon e.g. the designed wind pressure of a building. The averagethickness of the substrate layer is preferably at least 1 mm, morepreferably at least 2 mm, particularly preferably at least 3 mm. Theaverage thickness of the substrate layer is preferably at most 30 mm,more preferably at most 20 mm, particularly preferably at most 15 mm.When the average thickness is at least 1 mm, the substrate has highdurability, and the present optical layer is hardly broken. When theaverage thickness is at most 30 mm, the present optical layer is lightin weight, and the present solar cell module is more suitably used forthe wall surface or windows of a building.

The average thickness of the substrate layer is an arithmetic mean valueof the thicknesses measured by a thickness meter.

The substrate layer may be a layer obtained by surface-treating thematerial, in view of the adhesion to a layer other than the substratelayer. The surface treatment method may be a known method, such asactivation treatment (plasma method, deposition method, acid treatmentor base treatment), chemical conversion, polishing of the materialsurface, sander treatment, sealing treatment, blasting treatment orprimer treatment.

The substrate layer is particularly preferably a layer comprising asurface-treated glass plate. In such a case, a surface treatment methodis preferably primer treatment (particularly application of a primeragent).

The primer agent may, for example, be a silane coupling agent(particularly an alkoxysilane or the like), a titanium coupling agent,an epoxy resin, a (meth)acrylic resin or a polyester resin, and in acase where the material to be surface-treated is a glass plate,preferably a silane coupling agent or a titanium coupling agent.

The silane coupling agent is, in a case where the functional layer is alayer formed of the composition (1), in view of the adhesion to thesubstrate layer and durability, preferably a compound having from 3 to 4alkoxy groups or isocyanate groups as hydrolyzable groups and from 0 to1 non-hydrolyzable group bonded to a silicon atom. The non-hydrolyzablegroup is preferably an alkyl group which may have a functional group,and the functional may, for example, be an amino group, an isocyanategroup, a hydroxy group or an epoxy group.

The silane coupling agent may, for example, be specifically3-isocyanatopropyltrialkoxysilane, 3-aminopropyltrialkoxysilane,methyltriisocyanatosilane or tetraisocyanatosilane, and as commercialproducts, ORGATIX SI-310, SI-400, manufactured by Matsumoto FineChemical Co., Ltd. may, for example, be used.

The titanium coupling agent is, in a case where the functional layer isa layer formed of the composition (1), in view of the adhesion to thesubstrate layer and the durability, preferably an alkoxy titanium ester,titanium chelate or titanium acylate, more preferably an alkoxy titaniumester derivative containing a titanium oligomer. The titanium couplingagent is particularly preferably a compound represented by(RO)_(x)(TiO)_(y/2) (wherein X and Y are each independently a positiveinteger). As commercial products, ORGATIX PC-620 and PC-601 manufacturedby Matsumoto Fine Chemical Co., Ltd. may, for example, be used.

When a glass plate having a silane coupling agent or a titanium couplingagent applied thereto is used as the substrate layer, even when thecomposition (1) (particularly the composition (1) containing afluororesin) is directly applied on at least one surface of thesubstrate layer, the adhesion between the substrate layer and thefunctional layer is excellent. Further, the adhesion between thesubstrate layer and the functional layer in a case where the presentoptical layer is dipped in water improves, and such is suitable for asolar cell module which is used outdoor.

The present optical layer has been described with reference to FIG. 1.The present optical layer should only have a functional layer, asdescribed above, and may not have the substrate layer. The presentoptical layer preferably has the substrate layer in view of the strengthof the present optical layer.

The present optical layer may consist solely of the functional layer.Further, the present optical layer may have a layer other than thefunctional layer within a range not to impair the effects of the presentinvention. The layer other than the functional layer may, for example,be a substrate layer, an adhesive layer or an air layer. Further, thepresent optical layer may have a plurality of functional layers, or mayhave a plurality of layers other than the functional layer. The presentoptical layer should only have the functional layer, and the order ofdisposition of layers which the present optical layer has can besuitably selected.

The adhesive layer may, for example, be a layer which makes two or morelayers which the present optical layer has be attached to each other.

The air layer may, for example, be a layer, in a case where the presentoptical layer is a bag-form film, which maintains the present opticallayer in a state expanding in a cushion form. On that occasion, solarcells may be installed in the interior of the present optical layer.

The present optical layer is disposed on the side of plane of incidenceof sunlight of solar cells. Usually, solar cells are not used alone, buta plurality of solar cells are aligned next to one another andelectrically connected in series or in parallel. Accordingly, typically,the present optical layer is disposed as a continuous plane relative tosuch a plurality of solar cells, and is present on the side of plane ofincidence of sunlight of such solar cells.

The present optical layer does not typically contain an encapsulantlayer to encapsulate solar cells. The present optical layer ispreferably laminated on the encapsulant layer (on the side of plane ofincidence of sunlight of the encapsulant layer), in view of moreexcellent effects of the present invention.

The present optical layer may have irregularities on the surface on theair side so as not to impair the effects of the present invention. Anembodiment of the present optical layer having irregularities on thesurface on the air side, may, for example, be an embodiment such thatthe present optical layer has the functional layer as the outermostlayer on the air side, and the functional layer contains a delusteringagent, or an embodiment such that the present optical layer has thesubstrate layer as the outermost layer on the air side, and thesubstrate layer is properly surface-treated e.g. by polishing.

FIG. 2 is a cross-sectional view illustrating an embodiment of thepresent solar cell module 20 (hereinafter sometimes referred to asembodiment 1). The embodiment 1 is preferred in that since the substratelayer is disposed as the outermost layer, the design can be imparted tothe present solar cell module while the texture of the substrate is madegood use of.

As shown in FIG. 2, the solar cell module 20 comprises an optical layer10 comprising a substrate layer 110 and a functional layer 120, aplurality of solar cells 14, an encapsulant layer 16 and a rearprotective layer 18. The optical layer 10 is laminated on theencapsulant layer 16, and is disposed on the side of plane of incidenceof sunlight 40 of the solar cells 14. All the plurality of solar cells14 are encapsulated in the encapsulant layer 16.

The optical layer 10 is used as an optical layer for a solar cell moduleand imparts the design and the weather resistance to the solar cellmodule 20.

In the embodiment 1, the functional layer is preferably a functionallayer in which the matrix is at least one member selected from afluororesin, a silicone resin and a sintered product obtained bysintering a glass frit composition, and in view of the adhesion to theencapsulant layer, preferred is a fluororesin or a silicone resin.

In the embodiment 1, the substrate layer is preferably a glass plate inview of durability of the optical layer.

Each of the solar cells 14 has a first light-receiving surface 14A and asecond light-receiving surface 14B facing the first light-receivingsurface 14A. Each solar cell 14 has a function to convert light energyreceived by the first light-receiving surface 14A and the secondlight-receiving surface 14B to electric energy. Each solar cell may havethis function only on the first light-receiving surface or on both thefirst light-receiving surface and the second light-receiving surface.

The solar cells in the present invention are preferably made of amaterial having spectral sensitivity in a near infrared region.Specifically, they may be silicon-based solar cells composed ofmonocrystalline silicon, polycrystalline silicon or the like, orcompound-based solar cells composed of e.g. GaAs, CIS, CIGS, CdTe, InP,Zn₃P₂ or Cu₂S. The solar cells are particularly preferably CIS solarcells or CIGS solar cells, which require no wiring and thereby achievesmore excellent design of the present solar cell module and can besuitably used as an outer wall material, and which is more excellent inthe power generation in the near infrared region. Further, in a casewhere the solar cells have wiring, in view of the design of the presentsolar cell module, the wiring is preferably colored, particularlypreferably colored black.

FIG. 3 is a graph illustrating a sunlight spectrum (solar energy) on theground and a spectral sensitivity curve of a monocrystalline siliconsolar cell.

As shown in FIG. 3, the monocrystalline silicon-based solar cell hashigh spectral sensitivity also in a long wavelength range at awavelength of higher than 780 nm. That is, it means that a solar cellmodule having both the design and the power generation efficiency can beobtained by using the present optical layer showing a high transmittancein a long wavelength region.

The encapsulant layer 16 has a function to encapsulate the solar cells14.

The material constituting the encapsulant layer in the present inventionmay, for example, be specifically an ethylene/vinyl acetate resin, anolefin resin, a polyvinyl butyral resin, an ionomer resin or a siliconeresin. The encapsulant layer typically preferably contains no inorganicpigment or the like in the present invention or if contains, in aproportion of less than 1 mass % to the resin, since it is required tohave adhesion to the solar cells and a protective effect.

The rear protective layer 18 is disposed on an opposite side of thesolar cells from the side of plane of incidence of sunlight in the solarcell module.

The rear protective layer in the present invention is preferably a layerwhich improves the strength and the light resistance of the solar cellmodule. As specific examples of the material constituting the rearprotective layer, the same materials as the materials constituting thesubstrate layer may be mentioned.

The rear protective layer is preferably black in view of the design ofthe present solar cell module. Specifically, the rear protective layeris preferably a black glass plate or a glass plate having black coatingapplied thereto.

FIG. 4 is a cross-sectional view illustrating an embodiment of thepresent solar cell module 20 (hereinafter sometimes referred to asembodiment 2). The embodiment 2 is preferred in that since thefunctional layer is disposed as the outermost layer, the texture of thefunctional layer can be made good use of.

As shown in FIG. 4, the solar cell module 20 comprises an optical layer10 comprising a substrate layer 110 and a functional layer 120, aplurality of solar cells 14, an encapsulant layer 16, and a rearprotective layer 18. The optical layer 10 is laminated on theencapsulant layer 16, and is disposed on the side of plane of incidenceof sunlight 40 of the solar cells 14. The plurality of solar cells 14are all encapsulated in an encapsulant layer 16.

In the embodiment 2, the functional layer is preferably a functionallayer in which the matrix is at least one member selected from the groupconsisting of a fluororesin, a silicone resin, and a sintered productobtained by sintering a glass frit composition.

Details of the respective layers in the embodiment 2 are the same as inthe embodiment 1, and their description is omitted.

FIG. 5 is a cross-sectional view illustrating an embodiment of thepresent solar cell module 20 (hereinafter sometimes referred to asembodiment 3). The embodiment 3 is preferred in that the present solarcell module is suitably used in a case where sunlight enters from bothsides, for example, for a fence.

As shown in FIG. 5, the solar cell module 20 comprises a first opticallayer 10A, a plurality of solar cells 14, a first encapsulant layer 16A,a second encapsulant layer 16B and a second optical layer 10B. In thefollowing description, the first optical layer 10A and the secondoptical layer 10B may sometimes be generally referred to as an opticallayer 10. Further, the first encapsulant layer 16A and the secondencapsulant layer 16B may sometimes be generally referred to as anencapsulant layer 16. The optical layer 10 is laminated on theencapsulant layer 16, and is disposed on the side of plane of incidenceof sunlight 40A and 40B of the solar cells 14. All the plurality ofsolar cells 14 are encapsulated in the encapsulant layers 16A and 16B.The first optical layer 10A comprises a substrate layer 110A and afunctional layer 120A disposed on the substrate layer 110A.

The first optical layer 10A is disposed on the side of a firstlight-receiving surface 14A of the solar cells 14 and the side of planeof incidence of sunlight 40A, and is bonded on the encapsulant layer16A. Further, the second optical layer 10B is disposed on the side of asecond light-receiving surface 14B of the solar cells 14 and is bondedon the encapsulant layer 16B.

The second optical layer 10B has a substrate layer 110B and a functionallayer 120B disposed on the substrate layer 110B. The substrate 110B andthe functional layer 120B are respectively the same as the abovesubstrate layer 110A and functional layer 120A, and their description isomitted.

In the embodiment 3, the functional layer is preferably a functionallayer in which the matrix is a fluororesin, a silicone resin or asintered product obtained by sintering a glass frit composition.

Details of the respective layers in the embodiment 3 are the same as inembodiment 1, and their description is omitted.

The present solar cell module has been described with reference to FIGS.2, 4 and 5. The present solar cell module is not limited to the aboveembodiments. That is, the present solar cell module may have at leastone optional layer (such as an adhesive layer or an air layer) within arange not to impair the effects of the present invention. Further, thepresent solar cell module is not limited so long as the present opticallayer is disposed on the side of plane of incidence of sunlight of thesolar cells, and the other lamination order is not limited.

For example, the present solar cell module may have an optional layerbetween the present optical layer and the encapsulant layer. Further, inthe present solar cell module, the solar cells may not be encapsulatedin the encapsulant layer.

In a case where a glass plate is used as the substrate layer, in view ofthe design of the present solar cell module and adhesion between theencapsulant layer and the optical layer, the embodiment 1 isparticularly preferred.

FIG. 6 is a plan view schematically illustrating an example of a solarcell array constituted by the present solar cell modules.

As shown in FIG. 6, a solar cell array 30 is constituted by a pluralityof rectangular solar cell modules 20 aligned in a plane and connected inseries or in parallel.

The installation site of the solar cell array of the present inventionmay, for example, be specifically the rooftop, the roof or the outerwall (for example, a wall surface or a window) of a building.

The solar cell array of the present invention, which is excellent in thedesign and the weather resistance, is preferably used for an outer wallmaterial of a building (for example, a wall surface or a window of abuilding). FIG. 6 shows an embodiment in which the solar cell array ofthe present invention is rectangular, however, the shape of the solarcell array of the present invention is not particularly limited.

The outer wall material for building of the present invention comprisesthe present solar cell module described above. Accordingly, the outerwall material for building of the present invention is excellent in theweather resistance, the design and the power generation efficiency. Theouter wall material for building may, for example, be specifically acurtain wall, a wall material or a window.

The building of the present invention comprises a solar cell module, andan optical layer disposed on the side of plane of incidence of sunlightof the solar cell module.

The solar cell module in the building of the present invention is notlimited, and may be a solar cell module provided with the presentoptical layer, or may be a standard solar cell module not having thepresent optical layer. The solar cell module in the building of thepresent invention is preferably a standard solar cell module in view ofthe power generation efficiency of the solar cell module. The solar cellmodule is typically a solar cell module comprising solar cells, anencapsulant layer encapsulating the solar cells, a surface protectivelayer disposed on the side of plane of incidence of sunlight of thesolar cells, and a rear protective layer disposed on the opposite sideof the solar cell from the plane of incidence of sunlight. The standardsolar cell module may be a single-sided light-receiving type ordouble-sided light-receiving type.

The building of the present invention specifically has, on the side ofplane of incidence of sunlight of the outer wall material for buildinghaving the solar cell module, the present optical layer optionally viaan intermediate gas layer. That is, the building of the presentinvention is a building having a double skin system, and comprises thepresent optical layer as an outer skin.

The building of the present invention is excellent in the design and isalso excellent in the weather resistance, whereby the design of thebuilding is maintained. Further, since electric power can be supplied byphotovoltaic power generation, energy saving is accelerated.

The optical layer in the building of the present invention is the sameas the above optical layer of the present invention, and its details areomitted.

The optical layer of the present invention according to an embodiment isan optical layer comprising a functional layer containing at least onetype of inorganic pigment and a matrix in which the inorganic pigment isdispersed, and a substrate layer comprising a glass plate, and havingthe functional layer laminated on at least one surface of the substratelayer, wherein the inorganic pigment has a maximum near infraredreflectance in a near infrared region ata wavelength of from 780 to1,500 nm of at least 50%, an average particle size of from 5.0 to 280.0nm and a specific surface area of from 5.0 to 1,000 m²/g.

The optical layer of the present invention, which is likely toselectively transmit near infrared light, is useful also as a protectivelayer of an equipment having an infrared sensor, an element forconstituting a member to introduce LiDER (Light Detection and Ranging)system, etc.

According to the present invention, an optical layer having a powergeneration efficiency of at least 25% (more preferably at least 30%,particularly preferably at least 40%) obtained by the evaluation methoddescribed in Examples and being excellent in the design and the weatherresistance described in Examples, can be obtained.

EXAMPLES

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted to specific Examples. Ex. 1 to 8,14, 15 and 17 to 25 are Examples of the present invention, and Ex. 9 to13 and 16 are Comparative Examples.

Ex. 1 <Production of Composition (1)>

A polymer solution F (a xylene solution of achlorotrifluoroethylene/vinyl ether copolymer (“LF-200” manufactured byAGC Inc., polymer concentration: 60 mass %, fluorine atom content ofpolymer: 27 mass %, hydroxy value: 52 mgKOH/g) (7.32 g), xylene (3 g), a1 ppm xylene solution of dibutyltin dilaurate (0.31 g) and an inorganicpigment (1.9 g) were added, and further 13 g of glass beads having adiameter of 1 mm were added, followed by stirring by a kneading machine(Awatori Rentaro, manufactured by THINKY CORPORATION) at 2,000 rpm for20 minutes. Then, a curing agent (CORONATE HX, manufactured by TOSOHCORPORATION) (0.81 g) was added, followed by stirring at 2,000 rpm forone minute, and the glass beads were removed, to obtain composition(1-1).

<Production of Optical Layer>

On one surface of a soda lime silicate glass plate (manufactured by AGCInc., 100 mm×100 mm) having an average plate thickness of 3.2 mm, thecomposition (1-1) was applied by an applicator. Then, the composition(1-1) was dried by heating in a thermostatic chamber at 25° C. for oneweek, to obtain optical layer (1-1) comprising a substrate layercomprising the glass plate and a functional layer (average thickness: 46μm, matrix: fluororesin) laminated on the substrate layer.

Ex. 2 to 13

In the same manner as in Ex. 1 except that the type of the pigment waschanged as identified in Table 1, functional layer-forming compositions(1-2) to (1-13) and optical layers (1-2) to (1-13) were obtained.

In Ex. 6, as the inorganic pigment, a Co—Al composite oxide (1.9 g) andtitanium oxide (0.57 g) were used. In Ex. 7, as the inorganic pigment, aCo—Al composite oxide (1.9 g) and zirconium oxide (0.57 g) were used.Titanium oxide and zirconium oxide are a white inorganic pigment havinga minimum visible reflectance of at least 40%.

In Ex. 13, no pigment was added.

Ex. 14

In the same manner as in Ex. 5 except that a white inorganic pigment wasadded in a content as identified in Table 2, composition (1-14) andoptical layer (1-14) were obtained.

Ex. 15

In the same manner as in Ex. 14 except that the type of the whiteinorganic pigment was changed as identified in Table 2, composition(1-15) and optical layer (1-15) were obtained.

In Table 2, the inorganic pigment A is a colored inorganic pigment, andthe inorganic pigment B is a white inorganic pigment. In Table 2, the“content” is a proportion (mass %) of the white inorganic pigment to thetotal mass of the colored inorganic pigment.

Ex. 16

In the same manner as in Ex. 1 except that the inorganic pigment waschanged to an organic pigment as identified in Table 1, composition(1-16) and optical layer (1-16) were obtained.

Ex. 17 <Production of Composition (2)>

Denatured ethanol (manufactured by Japan Alcohol Trading Co., Ltd.,SOLMIX (registered trademark) AP-11, mixed solvent containing ethanol asthe main component) (0.20 g), distilled water (18.7 g),phenyltriethoxysilane (manufactured by Shin-Etsu Silicone, KBE-103)(11.5 g), methyltrimethoxysilane (manufactured by Shin-Etsu Silicone,KBM-13) (26.1 g), a sol containing scaly silica particles (manufacturedby AGC Si-Tech Co., Ltd., SUNLOVELY LFS-HN050, concentration of scalysilica particles: 15 mass %, average maximum particle size of scalysilica particles: 0.5 μm, thickness of silica primary particles: 2.5 nm,aspect ratio of silica primary particles: 200) (38.9 g) and an inorganicpigment (3.84 g) were mixed in this order and stirred for 30 minutes. Tothe obtained solution, an aqueous nitric acid solution (nitric acidconcentration: 10 mass %) (0.72 g) was added, followed by stirring for60 minutes to obtain composition (2-1).

<Formation of Optical Layer>

On one surface of a soda lime silicate glass plate (manufactured by AGCInc., 100 mm×100 mm) having an average plate thickness of 5.0 mm, thecomposition (2-1) was applied by an applicator. Then, the composition(2-1) was dried by heating at 150° C. for 10 minutes and cured to obtainoptical layer (2-1) comprising a substrate layer comprising the glassplate and a functional layer (average thickness: 60 μm, matrix: siliconeresin, volume fraction of scaly silica particles in functional layer:24%) laminated on the substrate layer.

Ex. 18 <Production of Composition (3)>

A glass powder containing, as calculated as oxides, BaO (31%), B₂O₃(25%) and ZnO (13%) (thermal expansion coefficient: 105×10⁻⁷1° C., 50%particle diameter (D50): 4.7 μm, softening point: 530° C.) (22.5 g),cordierite (50% particle diameter (D50): 2.5 μm, 90% particle diameter(D90): 4.6 μm) (6.8 g) as a thermal expansion coefficient-adjustingagent, ethyl cellulose (1.2 g) as a binder,2,2,4-trimethylpentane-1,3-diol monoisobutyrate (6.3 g) and ethyleneglycol mono-2-ethylhexyl ether (2.5 g) as organic solvents, and aninorganic pigment (2.7 g) were mixed by a kneading machine (AwatoriRentaro, manufactured by THINKY CORPORATION) and dispersed by athree-roll mill to obtained composition (3-1).

<Formation of Optical Layer>

On one surface of a soda lime silicate glass plate (manufactured by AGCInc., 100 mm×100 mm) having an average plate thickness of 3.2 mm, thecomposition (3-1) was applied by an applicator. After application, thecomposition (3-1) was dried by heating at 120° C. for 25 minutes toremove the organic solvents, then dried by heating at 370° C. for 30minutes to remove the binder, and further dried by heating at 600° C.for 10 minutes to sinter the composition (3-1) to obtain optical layer(3-1) comprising a substrate layer comprising a glass plate and afunctional layer (average thickness: 50 μm, matrix: sintered productobtained by sintering the glass frit composition) laminated on thesubstrate layer.

[Pigment Used in Ex.]

Ex. 1: “Daipyroxide™ Blue #3490E” (trade name manufactured byDainichiseika Color & Chemicals Mfg. Co., Ltd., colored inorganicpigment)

Ex. 2: “Daipyroxide™ Red #8270” (trade name manufactured byDainichiseika Color & Chemicals Mfg. Co., Ltd., colored inorganicpigment)

Ex. 3: “Cappoxyt Yellow 4214X” (trade name manufactured by Cappelle,colored inorganic pigment)

Ex. 4: “Sicotrans Red L2817” (trade name manufactured by BASF, coloredinorganic pigment)

Ex. 5: “Blue CR4” (trade name manufactured by ASAHI KASEI KOGYO CO.,LTD., colored inorganic pigment)

Ex. 6: “Blue CR4” (trade name manufactured by ASAHI KASEI KOGYO CO.,LTD., colored inorganic pigment) and titanium oxide (manufactured byC.I. Kasei Co., LTD., white inorganic pigment)

Ex. 7: “Blue CR4” (trade name manufactured by ASAHI KASEI KOGYO CO.,LTD., colored inorganic pigment) and zirconium oxide (manufactured byAldrich, white inorganic pigment)

Ex. 8: zirconium oxide (trade name manufactured by Aldrich, whiteinorganic pigment)

Ex. 9: “Daipyroxide™ Black #3550” (trade name manufactured byDainichiseika Color & Chemicals Mfg Co., Ltd., colored inorganicpigment)

Ex. 10: “42-250A” (trade name manufactured by Tokan Material TechnologyCo., Ltd., colored inorganic pigment)

Ex. 11: Iron oxide (trade name manufactured by JUNSEI CHEMICAL CO.,LTD., colored inorganic pigment)

Ex. 12: Yellow iron sesquioxide (trade name manufactured by JUNSEICHEMICAL CO., LTD., colored inorganic pigment)

Ex. 14: “Blue CR4” (trade name manufactured by ASAHI KASEI KOGYO CO.,LTD., colored inorganic pigment) and zinc oxide (manufactured by SAKAICHEMICAL INDUSTRY CO., LTD., white inorganic pigment)

Ex. 15: “Blue CR4” (trade name manufactured by ASAHI KASEI KOGYO CO.,LTD., colored inorganic pigment) and “MIZUKASIL P-526” (trade namemanufactured by MIZUSAWA INDUSTRIAL CHEMICALS, LTD., white inorganicpigment)

Ex. 16: Organic pigment

Ex. 17: “Blue CR4” (trade name manufactured by ASAHI KASEI KOGYO CO.,LTD., colored inorganic pigment)

Ex. 18: “Blue CR4” (trade name manufactured by ASAHI KASEI KOGYO CO.,LTD., colored inorganic pigment)

[Evaluation Method]

The methods for measuring physical properties are as described above.

More detailed measurement methods and conditions will be describedbelow.

(Inorganic Pigment) <Average Particle Size>

A sample to be measured (e.g. the inorganic pigment) was poured intodistilled water in a concentration of 0.1 mass %, and a dispersing agent(Poiz 532A, manufactured by Kao Corporation) was added in an amount of 1mass % to the solid content to obtain a slurry. The obtained slurry wassubjected to ultrasonic treatment by a table ultrasonic cleaning machine(1510 J-MT, manufactured by Branson Ultrasonics, Emerson Japan Ltd.) for6 hours, and 10 minutes, 30 minutes and then every 30 minutes afterinitiation of the ultrasonic treatment, the volume-based cumulative 50%diameter (D50) was measured by a particle size distribution measuringapparatus (Nanotrac Wave II-EX150, manufactured by MicrotracBEL Corp.).Among the cumulative 50% diameters (D50) at 13 points, the smallestvalue was taken as the average particle size.

<L* Value, a* Value and b* Value>

The L* value, the a* value and the b* value of the inorganic pigment arecalculated from a diffuse reflectance spectrum obtained by measurementby diffuse reflectance method in accordance with JIS Z8781-4: 2013.

The diffuse reflectance spectrum was obtained by measuring the diffusereflected light at 5 nm intervals within a wavelength range of from 200to 1,500 nm, by holding a sample to be measured (e.g. the inorganicpigment) in a glass holder having a depth of 0.5 mm and covering thesample with a quartz cover by using a spectrophotometer (U-4100,manufactured by Hitachi High-Technologies Corporation). As a reference,barium sulfate (reagent, manufactured by KANTO CHEMICAL CO, INC.) wasused.

<Maximum Near Infrared Reflectance and Minimum Visible Reflectance>

As the maximum near infrared transmittance and the minimum visiblereflectance of the inorganic pigment, the maximum reflectance at awavelength of from 780 to 1,500 nm and the minimum reflectance at awavelength of from 400 to 780 nm were calculated from the above diffusereflectance spectrum.

(Average Visible Transmittance, Average Linear Visible Transmittance andAverage Near Infrared Transmittance of Optical Layer)

The total reflectance of the optical layer was measured at 5 nmintervals within a wavelength range of from 380 to 1,500 nm at ascanning rate of 1,200 nm/min by using a spectrophotometer (manufacturedby Hitachi High-Technologies Corporation, trade name: U-4100).

The optical layer was placed so as to be in contact with alight-receiving part of an integrating sphere, and set so that lightentered from the surface of the optical layer.

The light source switching was automatic, the switching wavelength was340.0 nm, the slit was fixed at 8 nm, and the sampling interval was 5nm.

Further, there was no detector switching correction, the detectorswitching wavelength was 850.0 nm, the scanning speed was 750 nm/min,the slit was automatically controlled, the Pbs sensitivity was 2, andthe light control mode was fixed.

The average linear visible transmittance was obtained as the arithmeticmean of the linear transmittances at 5 nm intervals in a visible regionat a wavelength of from 400 to 780 nm in the total transmittanceobtained by the above measurement.

The average near infrared transmittance was obtained as the arithmeticmean of the transmittances at 5 nm intervals in a near infrared regionat a wavelength of from 780 to 1,500 nm in the total transmittanceobtained by the above measurement.

(Power Generation Efficiency 1)

Taking the power generation contribution degrees of the visible light(400 to 780 nm) and the near infrared light (780 to 1,500 nm) of themonocrystalline silicon cell being 30% and 70%, respectively, theaverage visible transmittance and the average near infraredtransmittance were multiplied and added, to calculated the powergeneration efficiency of the monocrystalline silicon cell using a sodalime silicate glass plate (manufactured by AGC Inc.) having an averageplate thickness of 3.2 mm.

(Design)

The design of the optical layer obtained by the above Ex. was evaluatedbased on the following standard from the average linear visibletransmittance obtained in accordance with the above method. The lowerthe average linear visible transmittance, the more excellent theshielding properties and the more excellent the design.

<Evaluation Standard>

A: The average linear visible transmittance being less than 20%.

B: The average linear visible transmittance being at least 20% and lessthan 40%.

C: The average linear visible transmittance being at least 40%.

(Weather Resistance)

An accelerated weathering test was conducted in accordance with JISK5600-7-7 using Accelerated Weather Tester (manufactured by Q-PANEL LABPRODUCTS, model QUV/SE). The functional layer surface of the opticallayer was irradiated with ultraviolet light, and a color difference wascalculated in accordance with the following formula (1) with respect tothe optical layer before the test and the optical layer 2,000 hoursafter initiation of the test, and evaluation was made based on thefollowing standards.

Color difference=[(ΔL*)²+(Δa*)²+(Δb*)²]^(1/2)  Formula (1)

Symbols in the formula have the following meanings.

ΔL* is an absolute value of the difference between the L* value of theoptical layer before the test and the L* value of the optical layerafter the test.

Δa* is an absolute value of the difference between the a* value of theoptical layer before the test and the a* value of the optical layerafter the test.

Δb* is an absolute value of the difference between the b* value of theoptical layer before the test and the b* value of the optical layerafter the test.

<Evaluation Standards>

A: The color difference obtained in accordance with the formula (1)being less than 1.0.

B: The color difference obtained in accordance with the formula (1)being at least 1.0 and less than 1.30.

C: The color difference obtained in accordance with the formula (1)being at least 1.30.

The obtained results are shown in Tables 1 to 3.

TABLE 1 Functional layer Pigment (inorganic pigment or organic pigment)Maximum near Average Specific infrared particle size surface areaDensity Thickness Composition reflectance (%) (nm) (m²/g) (g/cm³) L* a*b* (μm) Ex. 1 Co—Al composite oxide 83.1 151.0 19.1 4.0 47.2 15.0 −49.346 Ex. 2 Iron oxide 72.6 167.0 56.6 4.9 37.8 9.8 7.3 35 Ex. 3 Yellowiron sesquioxide 76.4 108.0 49.5 3.6 47.4 8.0 20.2 43 Ex. 4 Iron oxide73.9 127.0 50.0 4.1 35.8 3.9 3.3 43 Ex. 5 Co—Al composite oxide 82.6128.0 50.0 4.2 44.5 19.3 −48.9 48 Ex. 6 Co—Al composite oxide 82.6 128.050.0 4.2 44.5 19.3 −48.9 43 Titanium oxide 82.8 102.0 13.9 4.2 92.4 −0.65.0 Ex. 7 Co—Al composite oxide 82.6 128.0 50.0 4.2 44.5 19.3 −48.9 43Zirconium oxide 82.6 131.0 11.9 5.7 100.0 −0.4 1.1 Ex. 8 Zirconium oxide82.6 131.0 11.9 5.7 100.0 −0.4 1.1 48 Ex. 9 Cu—Fe—Mn composite oxide 7.8107.0 22.6 4.8 32.7 0.2 −0.2 48 Ex. 10 Co—Al composite oxide 83.4 284.05.5 4.1 50.8 13.5 −45.5 58 Ex. 11 Iron oxide 85.0 397.0 2.5 5.2 45.016.0 8.2 34 Ex. 12 Yellow iron sesquioxide 96.0 432.0 4.7 4.3 73.0 5.947.7 38 Ex. 13 — — — — — — — — 50 Ex. 16 Organic pigment — — — — — — —44 Optical layer Average near Average visible infrared Power generationWeather transmittance (%) transmittance (%) L* a* b* efficiency 1 (%)Design resistance Ex. 1 36.9 54.6 29.5 14.8 −34.3 49.3 A A Ex. 2 8.252.6 30.5 9.1 4.5 39.3 A A Ex. 3 40.2 86.0 34.3 4.8 7.9 72.3 A B Ex. 414.9 70.7 28.6 5.6 3.9 53.9 A A Ex. 5 41.4 58.9 29.4 16.1 −34.9 53.7 B AEx. 6 34.6 43.5 42.6 21.5 −56.8 35.9 A B Ex. 7 18.1 52.5 32.0 18.5 −41.747.1 A A Ex. 8 42.2 59.2 72.5 1.1 −13.1 54.1 A A Ex. 9 0.0 0.0 23.5 1.6−1.4 0.0 A A Ex. 10 15.3 26.0 34.6 24.5 −49.7 22.8 A A Ex. 11 0.0 9.040.5 29.3 21.9 6.3 A A Ex. 12 1.8 19.0 67.0 9.0 54.0 13.8 A B Ex. 13100.0 100.0 — — — 100.0 C A Ex. 16 8.5 39.0 43.4 51.7 23.3 29.8 A C

TABLE 2 Functional layer Inorganic pigment B Maximum Minimum AverageSpecific near Inorganic visible particle surface infrared pigment AContent transmittance size area reflectance Density ThicknessComposition Composition (mass %) (%) Reflectance (nm) (m²/g) (%) (g/cm³)(μm) Ex. 5 Co—Al — — — — — — 48 composite oxide Ex. 6 Co—Al Titanium 3062.6 2.50 102.1 13.9 82.8 4.2 43 composite oxide oxide Ex. 7 Co—AlZirconium 30 100.0 2.21 131.0 11.9 100.0 5.7 43 composite oxide oxideEx. 14 Co—Al Zinc 100 92.4 2.00 209.0 3.0 100.0 5.6 45 composite oxideoxide Ex. 15 Co—Al Silicon 30 81.7 1.44 197.0 14.9 81.7 2.2 38 compositeoxide dioxide Optical layer Average near Power infrared generationtransmittance efficiency Weather (%) L* a* b* 1 (%) Design resistanceEx. 5 58.9 29.4 16.1 −34.9 53.7 B A Ex. 6 43.5 42.6 21.5 −56.8 35.9 A BEx. 7 52.5 32.0 18.5 −41.7 47.1 A A Ex. 14 41.2 44.1 22.1 −58.9 33.7 A AEx. 15 63.3 28.0 14.1 −32.0 57.9 A A

TABLE 3 Optical layer Average near Power Functional layer infraredgeneration Thickness transmittance efficiency Weather Matrix (μm) (%) L*a* b* 1 (%) Design resistance Ex. 5 Fluororesin 48 58.9 29.4 16.1 −34.953.7 B A Ex. 17 Silicone resin 60 67.0 27.0 13.7 −33.5 62.2 A A Ex. 18Sintered product 50 44.0 32.1 14.8 −35.1 40.7 A A obtained by sinteringglass frit composition

It is shown from Tables 1 to 3 that the optical layer comprising thefunctional layer containing the inorganic pigment and the matrix inwhich the inorganic pigment was dispersed, the inorganic pigment havinga maximum near infrared reflectance in a near infrared region at awavelength of from 780 to 1,500 nm of at least 50%, an average particlesize of at least 5.0 nm and at most 280.0 nm and a specific surface areaof at least 5.0 m²/g and at most 1,000 m²/g, was capable of forming asolar cell module excellent in the design, and the power generationefficiency and the weather resistance.

Ex. 21 <Production of Optical Layer>

On one surface of a soda lime silicate glass plate (manufactured by AGCInc., 100 mm×100 mm) having an average plate thickness of 3.2 mm, asilane coupling agent (3-isocyanatopropyltriethoxysilane) was applied byan applicator and dried at 120° C. for 12 hours to form a primer layer.Then, on the primer layer, the composition (1-5) prepared in Ex. 5 wasapplied and dried by heating in a thermostatic chamber at 25° C. for oneweek and cured to obtain optical layer (1-5A) comprising a substratelayer comprising the glass plate, the primer layer and a functionallayer (average thickness: 46 μm, matrix: fluororesin) in this order.

Ex. 22

In the same manner as in Ex. 21 except that the silane coupling agentwas changed to methyltriisocyanatosilane to obtain optical layer (1-5B).

(Warm Water Resistance)

Each of the optical layers (1-5), (1-5A) and (1-5B) was dipped in warmwater at 80° C. for 100 hours, and whether the functional layer waspeeled from the substrate layer or not was visually confirmed, andevaluation was made based on the following standards. The results areshown in Table 4.

S: No peeling.

A: A peeling area being at most 5%.

B: A peeling area being at least 5%.

TABLE 4 Ex. 5 21 22 Optical layer (1-5) (1-5A) (1-5B) Warm waterresistance B A S

As shown in Table 4, by using a specific silane coupling agent as theprimer, the adhesion of the functional layer to the substrate comprisingthe glass plate improved.

Ex. 23 <Production of Solar Cell Module>

Black back glass, an interlayer (ethylene/vinyl acetate resin,manufactured by Bridgestone Corporation, EVASKY S88), the optical layer(1-3) and solar cells (5BB PERC manufactured by NSP) were laminated andvacuum heat-bonded to obtain solar cell module (1-3) comprising the backglass, the solar cells included in an interlayer (encapsulant layer) andthe optical layer (1-3) in this order and having the substrate layer inthe optical layer being disposed as the outermost layer of the solarcells.

The solar cell module (1-3) was yellow, and was confirmed to haveexcellent design such that the solar cells were not visually recognizedwhen visually observed from the optical layer side.

Ex. 24, 25

Solar cell modules (1-4) (red) and (1-5) (blue) were obtained in thesame manner except that the optical layers (1-4) and (1-5) were usedinstead of the optical layer (1-3).

(Power Generation Efficiency 2)

Using a solar simulator, with respect to the solar cell modules (1-3) to(1-5) and high transmission glass, the short circuit current (I_(sc)),the open circuit voltage (V_(oc)) and the maximum output (P_(max)) wereobtained. The proportion of P_(max) of the solar cell module to P_(max)of the high transmission glass (P_(max) of solar cell module/P_(max) ofhigh transmission glass×100%)) was taken as the power generationefficiency 2.

(Visibility of Solar Cell)

Whether or not the solar cells were visually recognized when each of thesolar cell modules (1-3) to (1-5) when observed from a distance of 1 mwas confirmed. A case where the cells were visually recognized was ratedas B, and a case where the cells were not visually recognized was ratedas A.

The other analysis item was evaluated in the same manner as above.Further, details of the optical layers used in Ex. 23 to 25 are the sameas in Ex. 3 to 5. The results are shown in Table 5.

TABLE 5 Solar cell module Power generation Cell shielding Optical layerefficiency 2 (%) properties Ex. 23 (1-3) 72.3 A Ex. 24 (1-4) 53.9 A Ex.25 (1-5) 53.7 A

It is shown from Table 5 that the solar cell module comprising theoptical layer of the present invention is excellent in the design andthe power generation efficiency.

This application is a continuation of PCT Application No.PCT/JP2018/043281, filed on Nov. 22, 2018, which is based upon andclaims the benefit of priority from Japanese Patent Application No.2017-236991 filed on Dec. 11, 2017, Japanese Patent Application No.2018-045508 filed on Mar. 13, 2018 and Japanese Patent Application No.2018-045416 filed on Mar. 13, 2018. The contents of those applicationsare incorporated herein by reference in their entireties.

REFERENCE SYMBOLS

-   -   10: Optical layer    -   10A: First optical layer    -   10B: Second optical layer    -   110: Substrate layer    -   110A: First substrate layer    -   110B: Second substrate layer    -   120: Functional layer    -   120A: First functional layer    -   120B: Second functional layer    -   14: Solar cell    -   14A: First light-receiving surface    -   14B: Second light-receiving surface    -   16: Encapsulant layer    -   18: Rear protective layer    -   20: Optical layer-provided solar cell module    -   30: Solar cell array    -   40, 40, 40B: Sunlight

What is claimed is:
 1. An optical layer comprising a functional layercontaining an inorganic pigment and a matrix in which the inorganicpigment is dispersed, to be disposed on the side of plane of incidenceof sunlight of solar cells, wherein at least a part of the inorganicpigment is an inorganic pigment having a maximum near infraredreflectance in a near infrared region at a wavelength of from 780 to1,500 nm of at least 50%, an average particle size of from 5.0 to 280.0nm and a specific surface area of from 5.0 to 1,000 m²/g.
 2. The opticallayer according to claim 1, wherein the optical layer is a coloredoptical layer, and the above specific inorganic pigment is a coloredinorganic pigment.
 3. The optical layer according to claim 2, whereinthe colored inorganic pigment is an inorganic pigment having in theL*a*b* color space an L* value of from 5 to 100, an a* value of from −60to 60, and a b* value of from −60 to
 60. 4. The optical layer accordingto claim 2, which further contains a light scattering inorganic pigment(excluding the colored inorganic pigment) having a minimum visiblereflectance in a visible region at a wavelength of from 400 to 780 nm ofat least 40%.
 5. The optical layer according to claim 4, wherein thelight scattering inorganic pigment has a refractive index of from 1.50to 2.60.
 6. The optical layer according to claim 4, wherein the lightscattering inorganic pigment is an inorganic pigment having an averageparticle size of from 10.0 to 2,000 nm and a specific surface area offrom 2.0 to 1,000 m²/g.
 7. The optical layer according to claim 1,wherein the matrix is at least one member selected from a fluororesin, asilicone resin, and a sintered product obtained by sintering a glassfrit composition.
 8. The optical layer according to claim 1, which hasan average near infrared transmittance of from 10 to 100%, which is avalue calculated by simply averaging near infrared transmittances at 5nm intervals in a near infrared region at a wavelength of from 780 to1,500 nm.
 9. The optical layer according to claim 1, which further has asubstrate layer, and has the functional layer laminated on at least onesurface of the substrate layer.
 10. A method for producing an opticallayer, which comprises applying, to at least one surface of a substratelayer, a functional layer-forming composition at least containing aninorganic pigment having a maximum near infrared reflectance in a nearinfrared region at a wavelength of from 780 to 1,500 nm of at least 50%,an average particle size of from 5.0 to 280.0 nm and a specific surfacearea of from 5.0 to 1,000 m²/g, and at least one member selected from afluorinated polymer, a silane compound and a glass frit composition, toform a functional layer thereby to form an optical layer comprising thesubstrate layer and the functional layer disposed on at least onesurface of the substrate layer.
 11. An optical layer-provided solar cellmodule, comprising solar cells and the optical layer as defined in claim1, wherein the optical layer is disposed on the side of plane ofincidence of sunlight of the solar cells.
 12. The solar cell moduleaccording to claim 11, wherein the solar cells are CIS solar cells orCIGS solar cells.
 13. An outer wall material for building, comprisingthe optical layer-provided solar cell module as defined in claim
 11. 14.A building comprising a solar cell module, and the optical layer asdefined in claim 1, disposed on the side of plane of incidence ofsunlight of the solar cell module.
 15. An optical layer, which comprisesa functional layer containing an inorganic pigment and a matrix in whichthe inorganic pigment is dispersed, and a substrate layer comprising aglass plate, and has the functional layer laminated on at least onesurface of the substrate layer, wherein at least a part of the inorganicpigment is an inorganic pigment having a maximum near infraredreflectance in a near infrared region at a wavelength of from 780 to1,500 nm of at least 50%, an average particle size of from 5.0 to 280.0nm and a specific surface area of from 5.0 to 1,000 m²/g.